F.~' - v .

NWC TP 6676

00

Geothermal Potential ofAdak Island, Alaska

byAllan M. Katzenstein

andJames A. Whelan

Public Works Department

OCTOBER 1985

NAVAL WEAPONS CENTER DLETCCHINA LAKE, CA 935554601WIC E

,j~DEC 2 S85

Ap-p-oved for public release; distributionis unlimited.

85 11 26 009

Naval Weapons Center

FOREWORD

This report documents a study conducted from 1976 to 1982 of the potential forgeothermal energy development at Adak Island, Alaska. Adak is the site of the U.S. NavalStation, Adak, which depends on JP-5 jet fuel for all electrical power and space heating needs.The work, which was funded by the Naval Civil Engineering Laboratory, Port Hueneme,Calif., was performed by the Naval Weapons Center (NWC), China Lake, Calif. NWC, aslead Navy activity, conducts research to determine geothermal energy potential at navalinstallations and its viability as an energy resource.

Extensive geological, geophysical, and geochemical investigations were made on Adak, andtemperature measurements were obtained from two observation holes. Favorable results pointto the desirability of further drilling to verify the existence of an economic geothermal energysource.

This report was reviewed for technical accuracy by Carl F. Austin and Steven Bjornstad.

Approved by Under the authority ofR. M. CUGOWSKI K. A. DICKERSONCapt., CEC, USN Capt., USNPublic Workv Officer Commander1 October 1985

Released for publication byB. W. HAYSTechnical Director

NWC Technical Publication 6676

Published by ....................................... [echnical Information DepartmentC ollation .................... ...................................... C over, 47 leavesFirst printing ............................................................. 150 copies

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SECuRITY CI AS- 1FICATION OF THIS PAGE

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Approved for public release; distribution2b OECLASSIFICATION /DOWNGRADING SCHEDULE is unlimited.

4 PERFORMING ORGANIZATION REPORT NUMBER(S) 5 MONITORING ORGANIZATION REPORT NUMBER(S)

NWC TP 66766a NAME OF PERFORMING ORGANIZATION 6b OFFICE SYMBOL 7a NAME OF MONITORING ORGANIZATION

(If applicable)

Naval Weapons Center I6c ADDRESS (City, State, and ZIP Code) 7b ADDRESS (City,. State, and ZIP Code)

China Lake, CA 93555-6001

8a NAME OF FUNDING/SPONSORING 8b OFFICE SYMBOL 9 PROCUREMENT INSTRUMENT IDENTIFICATION NUMBERORGANIZATION (If applicable)

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11 TITLE (Include Security Classification)

GEOTHERMAL POTENTIAL OF ADAK ISLAND, ALASKA (U)

12 PERSONAL AUTHOR(S)

Katzenstein. Allan -M. and Whelan, James A.13a TYPE OF REPORT 13b TIME COVERED 14 DATE OF REPORT (Year, Month, Day) 15 PAGE COUNT

Interim FROM 1976 TO 1982 1985, October 92

16 SUPPLEMENTARY NOTATION

17 COSATI CODES 18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number)

FIELD GROUP SUB-GROUP Adak Island, Alaska Geothermal potential08 04 Geochemistry Microseismic studies08 07 Geophysics Observation drill holes

19 ABSTRACT (Continue on reverse if necessary and identify by block number)

(U) The U.S. Naval Station, Adak, Alaska, is dependent on JP-5 jet fuel for all power and space heating requirements.In the Navy's continuing program to explore alternative enegy sources, investigations have been undertaken into the geothermalpotential of Adak Island. Extensive geological, geophysical, and geochemical investigations and the results obtained fromdrilling observation holes indicated that a geothermal potential exists. Further drilling should be accomplished to verifywhether an economic geothermal resource can be developed.

20 DISTRIBUTION/AVAILABILITY OF ABSTRACT 21 ABSTRACT SECURITY CLASSIFICATION

(3UNCLASSIFIED/UNLIMITED 0 SAME AS RPT 0 DTIC USERS UNCLASSIFIED22a NAME OF RESPONSIBLE INDIVIDUAL 22b TELEPHONE (Include Area Code) 22c OFFICE SYMBOL

A. M. Katzenstein (619) 939-3411, x471 NWC Code 2661

DD FORM 1473,84 MAR 83 APR edition may be used until exhausted SECURITY CLASSIFICATION OF THIS PAGEAll other editions are obsolete UNCLASSIFIED

,. -........... .. W..,' UNCLASSIFIED.* . .. .

Accesloi.F'

NWC TP 6676 Una,-C. _

St i tjo

i. i 1ity C,,ode s

A\vui, a d orCONTENTS 'Jt pcciaI

Introduction..................................... - 3

Geography............................................................... 3

History................................................................... 6

Geoscientific Investigations .................................................. 7Geology.............................................................. 7Geochemistry of Hot and Warm Springs .................................... 10Chemical Geothermometry .............................................. 12Hydrothermal Alteration................................................ 14

Andrew Bay Hot Springs ............................................ 14Kikuga Warm Springs............................................... 14

Previous Geophysical Studies............................................. 15Aeromagnetics .................................................... 15Microearthquakes I................................................. 15Electrical Surveys I................................................. 19Electrical Surveys II................................................ 20Gravity I......................................................... 23

Observation Hole Drilling............................................... 25Additional Geophysical Studies ........................................... 26

Gravity II........................................................ 27Land Magnetics ................................................... 30

Soil Geochemistry ..................................................... 32Microearthquakes II . ................................................. 34Aerial Photography Interpretation......................................... 36Other Observations .................................................... 38

Summary and Discussion ................................................... 38

Conclusion .............................................................. 40

References............................................................... 41

Appendixes:A. Geological Techniques, Evaluation of' Geothermal Potential

of Adak Island, Alaska .... .......................................... 43B. Thin-Section Descriptions, Samples Fromn Andrew Bay Hot Springs

and Kikuga Warm Springs................. ........................... 71

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fl C. Temperature Log, Adak Island Drill Holes ................................... 79D. Gravity and Magnetic Facts, Northern Adak .................................. 81E. Mercury Content of Soil Samples, Northern Adak ............................. 89

ACKNOWLEDGEMENTS

The authors express their appreciation to Captain Allender, Commander of the Naval AirStation, Adak, Alaska, and to the numerous Public Works officers who provided untiringassistance to the field crews and made field work on Adak bearable. Thanks also for the help(and humor) of many military and civilian personnel on the island.

Special thanks to Terry AtienzaMoore for keeping the '82 field crew organized (andentertained) and for all her help; and thanks to Jack Neffew, Jeff Roquemore, Dawn Janney,Ron Clodt, and Carl Halsey for help in the field and to Carla Gerrard for help in the office.

And last but not least, thanks to Steve Bjornstad and Ben Swanr for their excellent

drafting of figures and to Carole Anderson for her editing and comments.

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INTRODUCTION

Adak Naval Station, Adak, Alaska is located approximately 1,200 miles southwest ofAnchorage and 700 miles southeast of Siberia, near the center of the Aleutian island chain. TheStation is strategically important for patrol and surveillance of Arctic waters. On Adak, allelectric power generation and space heating is done with JP-5 jet fuel, amounting to nearly9 million gallons per year. This dependence on oil, coupled with the remoteness of the island,makes any form of indigenous power source attractive if it is exploitable commercially. Thepurpose of this report is to present the data, results, and interpretations of numerousgeoscientific investigations concerning indigenous geothermal potential at the Naval Station(NAVSTA), Adak.

GEOGRAPHY

Adak Island is located near the middle of the Aleutian chain in the Andreanof Islands(Figure 1). The island is roughly 30 miles east to west, 20 miles north to south (289 squaremiles), has 212 miles of shoreline, and is the largest island in the central Aleutian chain.

Most of the island is mountainous and rugged, and it has an irregular shoreline marked bynumerous bays and indentations (Figure 2). Southern Adak, while rugged, probably containsglacially dissected marine platforms and is pocked by numerous small stream-fed lakes(Reference 1). Yakak Peninsula, an area of extensive lowlands, probably resulted frompreglacial wave planation modified by stream and glacial erosion. The eastern coast ischaracterized by steep bluffs and rocky cliffs. Mount Moffett rises nearly 3,900 ft on thenorthwest end of the island, while Mount Adagdak rises to over 2,000 ft on the northeast side.In between the two mountains lie the remnants of the Andrew Bay Volcano. Also promiaenton the northern end of the island are the large freshwater lake, Andrew Lake; the saltwaterembayment, Clam Lagoon; and the open-water indentations of Kuluk Bay and Sweeper Cove.Finger Bay, structurally controlled by the Finger Bay Fault, lies south of Sweeper Cove.

Adak has the maritime climate common to all the Aleutian Islands of persistently foggy,wet, and stormy weather. The cloud ceiling on the island can range from 1,000 to 3,000 ft,and precipitation occurs almost every day, normally in great quantity. Located within theNorth Pacific storm tract, the island is frequently buffeted by intense storms, which producewinds in excess of 50 knots (although this is just a little brisker than the normal, day-to-daywind, which ranges from 10 to 33 knots). However, because of the moderating nearby warmJapanese current, the average annual temperature of the island is cool but not severe. Theaverage monthly temperatures of Adak range from 0°C in February to 11C in August.

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The volcanic nature of the Adak soil, coupled with the short growing season and lowaverage summer temperature, retards tree and vegetable growth. On the other hand, tundra, afoot-high grass with a spongy base, grows well. During the summer the entire island is coveredwith a green carpet of tundra spotted with wildflowers. During the rest of the year, the tundradies back to an all-encompassing and, some consider, a depressing brown.

Adak is the headquarters for the Aleutian Islands National Wildlife Refuge. The refuge of2,720,235 acres comprises nearly 70 named islands of the Aleutian chain. The southern half ofthe island belongs to the refuge (see Figure 2). Birds are the most obvious feature of the refuge;the bald eagle is resident in substantial numbers. A large herd of caribou on Adak is the directresult of transplantation from the mainland and careful management. Also, the streams issuingfrom the island are used by large numbers of spawning salmon, to the point of overspawning,during the summer months. Sea otters are abundant in the coastal coves and in Clam Lagoon.

HISTORY

Adak is believed to have been first settled by the Aleuts, who supposedly crossed theprehistoric land bridge from Asia. The Aleuts were an easygoing, good-natured people;numbering from 20,000 to 25,000, they located in hundreds of island villages along theAleutian chain. On 9 September 1741, the Russian vessel St. Paul, commanded by CaptainAlexei Chirikof, anchored in a small open bay on the south coast of Adak and officiallydiscovered the island. Later, Cossack fur traders descended on the Aleutian Islands, demandingtributes of furs and forcing their way of life on the friendly natives. The Aleuts scattered; andensuing battles, plus open massacres by the Russians, decimated the Aleut population until onlya handful of colonies survived.

Adak became part of the United States in 1867, when Secretary of State William HenrySeward persuaded Congress to purchase the Alaskan Territory from the Russians. The purchaseat $7,200,000 seemed extravagant for such a barren wasteland, and the action became knownas "Seward's Folly." Now, 7 million dollars would not even pay the fuel bill to provide heatand electricity to NAVSTA for 1 year.

World War II came to the Aleutian chain in June of 1942, when the Japanese bombedDutch Harbor and Unalaska. They occupied the islands of Attu and Kiska at the western endof the chain. Navy patrol planes from Atka and bombers from Dutch Harbor made longharassment flights against the Japanese on these islands, but had little effect when the numberof planes lost to inclement weather was considered. The fleet commanders decided that a basenearer these islands would be necessary if the Japanese were to be driven from the Aleutians.Adak was chosen as the most likely site, and on 28 August 1943 it was occupied by Americantroops.

In 10 days, Seabees and Army Engineers constructed a landing strip for fighter planes andbuilt a staging base that eventually supported 90,000 American troops. Fighters and bombersfrom Adak weakened the Japanese defenses on Attu prior to an invasion by American troops.Bloody combat with the hard-core Japanese troops lasted nearly 2 weeks before the Japanesesurrendered.

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A joint Army-Navy team surveyed Adak Island in 1946 to establish a permanent Navybase. After the war, until 1948, Adak was operated by the Air Force but controlled by theArmy. In July 1950 NAVSTA, Adak was commissioned. In 1951, the U.S. NavalCommunications Station (COMSTA) was established; subsequently, in 1977, COMSTA wasrenamed the Naval Security Group Activity (NAVGRUSECACT). In 1971, the Fleet Air AlaskaCommand was transferred from Kodiak Island to Adak. The base now includes a navalfacility, Marine battalion, Patrol Wings Pacific detachment, weather detachment, explosiveordnance detachment, and patrol squadron detachment. A seismology laboratory, maintainedby the University of Colorado, and the wildlife refuge are tenant activities.

The mission of NAVSTA, Adak is to provide support for the antisubmarine warfareprogram and to conduct search and rescue operations in the North Pacific. AlsoNAVGRUSECACT serves as a key link in the Navy's communications network. The populationof Adak, including NAVSTA, NAVGRUSECACT, the Naval Facility, the Alaska State SchoolSystem, the scientific community, the U.S. Fish and Wildlife Service, and contractors, isbetween 4,500 and 5,000 military personnel, dependents, and civilians.

GEOSCIENTIFIC INVESTIGATIONS

GEOLOGY

Bradley pro-ided the first significant geologic study of Adak Island when he published his"notes on geology" that he made while stationed on the island in the mid-1940s (Reference 2).While his study was not intensive, he did note the northward shift in volcanic activity, citedthree periods of volcanism on the island, and commented on the glaciation and structure of theisland. He did not, however, provide a geologic map.

Coats spent 25 days in the field in 1946 to prepare the geologic map most commonlyaccepted for northern Adak Island (Reference 3). This map is reproduced as Figure 3 in thisreport. Coats recognized two physiographic and geologic divisions on the mapped part of theisland: (1) a southern area comprising folded, faulted, and intensely altered volcanic rocks ofPaleozoic age that were deeply glaciated and then intruded by rocks of younger gabbroic andintermediate composition; and (2) a northern area dominated by three distinct volcanoes(Andrew Bay Volcano, Mount Moffett, and Mount Adagdak) of Tertiary or Quaternary age.Near the central part of the map are five volcanic domes of light-colored andesite porphyrythat Coats feels are separate from the three basaltic volcanoes and probab!y are of earlyTertiary age. The volcanoes have been trimmed by marine erosion and dissected by subaerialand ancient glacial erosion and have minor amounts of sedimentary rocks associated withthem. The lowland areas of the island are covered by a blanket of ash from volcanoes on other,nearby islands.

An excellent summary of geology relating to a possible geothermal resource is anunpublished report by Miller and Smith (1977). Miller and Smith's work is sufficientlyimportant that, rather than paraphrasing their findings in small sections, this report includesthe entire summary as an appendix. Of particular interest are the sections on regional geologicsetting, local geology, geochronology, and petrology that can be found in Appendix A.

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EXPLANATIONA WIDESPRlIAD THIN ILANKET OF WILL-STeATiIID BASALTIC ASH AND PULIICtNOT SHOWN ON NAP

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9

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GEOCHEMISTRY OF HOT AND WARM SPRINGS

Miller and Smith (Appendix A) give a good description of the hot and warm springs onAdak Island. Another good description of the springs is given by James L. Moore andW. R. Tipton of the California Energy Company, Inc. (CECI). Moore and Tipton visitedAdak in the summer of 1981 to evaluate the geothermal potential of the island. Moore'sdescription of the Andrew Bay Hot Springs (see Figure 2) is quoted from Reference 4 with theauthor's permission:

"On Friday, July 31, I visited the hot spring located on the northwest coast of Mt.Adagdak, northerly off the NE corner of Andrew Lake (51058'N, 176038'W). This particularspring is already noted in the literature. However, it should be noted that the surfacePxpression of the active spring is significantly different from the description in the literature.These surface changes can probably be attributed to an extremely severe storm that occurredduring December of 1980.

"The large hot pool noted by others is gone, and the only geothermal evidence remainingis a series of small gas vents and hot water springs. The measured spring temperature was155°F, pH was 5.5, field titration for CO2 yielded 668 ppm and field titration for HCO3yielded 512 ppm. The springs are issuing from a group of vertical NW trending fracturesextending across approximately 150 feet of basic igneous rock. One significant feature of thearea near the springs was the abundance of dead and decaying marine vegetation; apparentlythe result of geothermal emissions. A similar concentration of dead and decaying marinevegetation was noted approximately one mile northerly along the beach (51059'N, 176037'W).Although no direct evidence of geothermal emissions were noted, the concentration of the dead

" marine materials indicated the probable presence of geothermal fluids."

The CECI analyses of the Andrew Bay Hot Springs water and of seawater from AndrewBay given in Reference 4 are listed in Table 1.

Persistent rumors of hot springs on Mount Moffett led Moore in 1981 to explore the surfaceon and around that mountain. He discovered warm springs at Cape Kiguga on Mount Moffett(refer to Figure 2). His description of these springs follows. An analysis of water from thesesprings, also from Reference 4, is given in Table 1.

"On Saturday, a traverse was made to a point on the beach approximately one milesoutherly of Cape Kiguga (51054'N, 176047'30"W). The beach deposits southerly of the subjectpoint consisted of rounded boulders of fresh volcanic materials one to four feet in diameter.However, it was also noted that for a distance of approximately one to one and a half milessoutherly of the gas seep/hot springs, silicified and calcified rocks were seen along the beach.

"The 'hot spring' consisted of fractured volcanics from which warm water and CO2 wereescaping. The fractures were vertical and oriented parallel with the beach in a $450Edirection. Measured temperature was 60'F, pH was 4.5. Dissolved CO2 = 870 ppm withHCO3 at 36 ppm. Marine vegetation was absent from the immediate spring areas. Iron springswere present along the margins of the main spring area and also extended southerly forapproximately one mile along the beach. Basic exposure above the beach consisted of glacialdrift (till)."

Also, during Moore's visit in 1981, there were persistent rumors of warm or hot springs onLucky Point, between Sweeper Cove and Finger Bay. On 29 July 1981, J. Whelan and

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TABLE 1. Chemical Analysis, Andrew Bay Hot Springs. Kiguga Warm Springs, andAndrew Bay Seawater.

Andrew Bay Hot Springs Kiguga Springs

Value Seawater

measured USGS USGS CECI CECI NAVY CECI3

76AMm220 a 76AMm221a 1 2 1

Dilution ? ? 1:7 1:6 ......pH 7.4 7.5 ... ... 7.0

Specific conductance,pmho/cm ... ... > 10.000 3,900 ... > 10,000

Temp. (meas.),°C 63 71 ... ... ... ...

Constituent, ppmbCalcium 1500. 1300. 1300. 21. 13. 290.Magnesium 70. 110 460. 38. 7. 340.Sodium 6800. 6100. 5800. 500. 72. 6800.Potassium 460. 380. 460. 38. 5.1 340.Carbonate 0Bicarbonate 420. 430. 85.8Chloride 14000. 1100. 93.5 15000.Sulfate 120. 330. 350. 200. 21. 2300.Nitrate 4.0Fluoride 0.49 0.55 0.6 0.26 0.08 0.83Iron 3.8 0.87 < 0.05 0.20Manganese < 0.01Arsenic < 0.01Copper < 0.01Zinc 0.01Mercury < 0.0002Silica 192. 15.0 36 ...Aluminum < 0.2Boron 87. 70. 89.0 0.39 0.06 3.5Phosphate 0.2Bromine < 0.2Lithium < 0.01Nitrite < 0.002Ammonia N 1.5 3.1 > 0.22Ammonium ... c

Ammonium (bycalculation)l 1.9 4.0 > 0.26

Hydroxide none

a Refer to Appendix A.b ppm - parts per million.C Insufficient sample.d Calculation of amount of ammonium expected at the time sample was taken in the field. Derived

from the value of ammonium detected in the laboratory.

R. Clodt, of the Naval Weapons Center (NWC), China Lake, Calif., joined Moore in exploringthe Lucky Point area. Moore's description is given below:

"On Wednesday, July 29, a traverse was made to Lucky Point (51°51'N, 176 035'W), apeninsular parcel of land between Sweeper Cove and Finger Bay. It was reported that hotsprings were located somewhere along the north coastal portion of the point. The entire pointarea was examined for approximately the easterly-most mile of the peninsula and no evidenceof active hydrothermal activity was defined. A small amount of surface discoloration and

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extremely minor CaCO3 precipitation was noted on the rocks immediately above sea waterlevel in a little cove about one mile west of the point (51'51'N, 176'36'30"W). This site is notbelieved to represent any 'real' surface manifestation of geothermal activity. No direct evidenceof active geothermal activity was found anywhere on the peninsula and the reported 'hotspring' was in all likelihood one of the numerous very shallow tundra lakes that dot thepeninsula's surface that had been warmed by the sun to a temperature that was pleasant to theI'skinny dippers'."

Reports of surfur-bearing fumaroles on the upper slopes of both Mount Moffett and Mount

Adagdak were not evaluated in the field.

CHEMICAL GEOTHERMOMETRY

Hot and warm springwater geochemistry is valuable in evaluating geothermal resources.Calculations were made at the Andrew Bay Hot Springs and Kiguga Warm Springs todetermine temperatures of var:ous geothermometers. Results are given in Table 2.

TABLE 2. Chemical Geothermometers, Andrew Bay Hot Springs, Kiguga Warm

Springs, and Andrew Bay Seawater.

Andrew Bay Hot Springs Kiguga SpringsGeother- 1SeawaterGeothr- aCECImometer0

USGS USGS CECI CECI NAVY 376AMm220b 76AMm221b 1 2 1 3

Values in O _

a 174 173 167 62 91 ...b 186 185 177 54 87 ...c 165 164 155 20 54d 149 142 164 160 153 123e 188 182 194 185 82 185f ... ... ... 162 ... 169g 187 181 . ... ... . ...

a Geothermometers:

a-Quartz, steam flashing (Fournier, 1981, Reference 5).b-Quartz, conductive cooling (Fournier, 1981, Reference 5).c-Chalcedony, conductive cooling (Fournier, 1981, Reference 5).d-Sodium-potassium (Truesdell, 1976, Reference 6).e-Sodium-potassium-calcium (Fournler and Truesdell, 1973, Reference 7).f-Sodium-potassium-calcium-magnesium (Fournier and Potter, 1979,

Reference 8).g.-Sdium-potassium-calcium-carbonate (Paces, 1975, Reference 9).

b Refer to Appendix A.

Of interest is the general .greement between the silica, quartz conductive coolingtemperature and the sodium-potassium-calcium temperatures for the Andrew Bay Hot Springs.Because of possible seawater encroachment, the writers believe the silica geothermometers to bemost appropriate, with either the quartz conductive cooling or the chalcedony conductivecooling applying. Therefore, our best estimate of reservoir temperature for the Andrew BayHot Springs is 155 to 186°C. For the Kiguga Warm Springs the temperatures would range from54 to 91°%C.

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The calculated temperatures stated above compare well with those published by Motyka(Reference 10). He calculated temperatures of 160 to 188°C for the deep reservoir temperature.Motyka also states (in a personal communication) that there is a magmatic influence on thehydrothermal system. He determined this influence by use of helium (3He/ 4He) and analyses of13C in fumarolic C02.

Because of high precipitation on Adak, it was decided to try "mixing models." The silicamixing model of Truesdell and Fournier is shown as Figure 4 (Reference 11). The Kigugasprings were used as groundwater; the Andrew Bay springs as the warm spring. Since the linethrough the Kiguga point and the Andrew Bay points does not intersect the quartz solubilityline, the "no steam loss" model does not apply. Assuming that enthalpy in international tablecalories per gram has nearly a one-to-one correlation to temperature in this range of 0C,* and

900 I I I

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0 00 200 300ENTHALPY, IN INTERNATIONAL TABLE CALORIES PER GRAM

FIGURE 4. Silica Mixing Mode. of Truesdell and Fournier (1979) Applied toGeothermal Waters, Northern Adak Island.

Refer to steam tables in a Handbook of Chemistry and Physics. for example.

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assuming a steam loss at 100'C and one atmosphere pressure, the reservoir temperature wouldbe 190'C. Based on equations from Fournier (Reference 12), the silica content of the reservoirwould be about 220 ppm and there would have been a 21 % steam loss. There are not enoughdata to apply the chloride mixing model.

HYDROTHERMAL ALTERATION

Geothermal solutions interact chemically with the rocks they traverse, depositing new

minerals in fractures and replacing rock minerals. Opal, chalcedony, quartz, calcite, aragonite,pyrite, marcasite, sulfur, realgar, orpiment, and cinnabar are frequently deposited. Earlierrock-forming minerals may be changed to chlorite, epidote, serpentine, alunite,montmorillonite, kaolin family minerals, secondary biotite, K-feldspar, etc. Both the AndrewBay Hot Springs and the Kiguga Warm Springs areas exhibit hydrothermal alteration. Samplescollected by Brophy were studied petrographically (Reference 13). Individual thin-sectiondescriptions are given in Appendix B.

Andrew Bay Hot Springs

Four thin sections from the Andrew Bay Hot Springs area were studied. Three of the thinsections were andesites and the fourth an andesite porphyry breccia (see Appendix A). Allsections exhibited hydrothermal or deuteric alteration.

The fine-grained groundmass (0.03 to 0.5 mm) seen in the thin sections make up 60% ofthe rock and consist mostly of plagioclase with minor amounts of quartz, calcite, and epidote.In the breccia sample, the andesite fragments are cemented by limonite.

Phenocrysts are hornblende and plagioclase. Hornblende phenocrysts range in size from0.6 to 3 mm; all have been at least partially altered to chlorite and epidote. In the moreseverely altered rocks the transformation is complete. Plagioclase phenocrysts are euhedral andrange from 0.5 to 4 mm. They are severely fractured and exhibit oscillatory zoning. Often theyhave several optical orientations and overgrowths. They are calcie and when altered arepartially replaced by calcite and sericite. Miller and Smith (Appendix A) also noted augite insimilar samples, but none was found during this study.

Pyrite is present in all but the least altered sample and varies in crystal form fromanhecral to euhedral. The anhedral pyrite is fine grained, about 0.01 mm, while euhedral

pyrite in the more altered samples is up to 0.6 mm. The anhedral pyrite may representsulfidized magnetite.

Kiguga Warm Springs

Three thin sections of breccia associated with the Kiguga Warm Springs were prepared.The fragments in the breccia appear to be a tuff or tuffaceous sandstone. Microscopicexamination indicated a groundmass or matrix consisting of glass (0.01 mm including shards),quartz (0.05 to 0.15 mm), and K-feldspar. Microphenocrysts consist of euhedral K-feldsparranging from 0.25 to 1 mm and making up about 25% of the rock; anhedral quartz averaging0.25 mm, making up 30% of the rock; and a few percents of euhedral-zoned plagioclase

14

, €.'~' ~ ~

NWC TP 6676

ranging in size from 0.2 to 0.6 mm; thus, the fragments are rhyolite from an unknown source.The cement of the brecia is chalcedony.

The rock weathers tan, with areas containing pyrite going to brown because oflimonitization. Hydrothermal alteration has sericitized the feldspars and probably some of theglass. Sericitization ranges from moderate to severe. Both euhedral and anhedral pyrite, incrystals and patches up to 0.2 mm, have been introduced. Quartz veinlets cut through therock, and barite has possibly been introduced.

Of the two springs, the hydrothermal alteration of the Andrew Bay Hot Springs is bothless intense and less apparent visually than that at Kiguga Warm Springs because the softhydrothermal alteration minerals are easily eroded from the wave-cut terrace where theyoccur. The alteration of the Andrew Bay Hot Springs is essentially propylitic, with theintroduction of pyrite and the conversion of magnetite to pyrite. This pyritic conversionprobably accounts for a magnetic low seen by an aeromagnetic survey described in a latersection. The alteration at Kiguga Warm Springs is more severe phyllitic (sericitic) alteration,with the introduction of quartz, chalcedony, and pyrite into the rock.

PREVIOUS GEOPHYSICAL STUDIES

Aeromagnetics

An aeromagnetic survey was flown over northern Adak Island in 1948, and the resultswere reported by Keller, Meuschke, and Alldredge (Reference 14). The survey was flown at anelevation of 5,000 ft (1.5 kin) and a spacing of 1 mile (1.6 km). Observed data are shown onFigure 5, and a second derivative is shown on Figure 6.

On Figure 5, a large anomaly of approximately 700 gammas is seen south of Finger Bayand is ascribed by Keller to the large mass of gabbro in that area. Anomalous highs, associatedwith the volcanic domes on Mount Adagdak and the cone of olivine-basalt on Mount Moffett,are seen on both Figure 5 and Figure 6, as is the magnetic low over Kuluk Bay (although onlyslightly on the second derivative map). Keller points out that the low over Kuluk Bay may notrepresent a great thickness of sediments. The low may represent a function, characteristic ofmagnetics in the higher magnetic latitudes, where a well-defined low forms directly north of amagnetic high; e.g., the Finger Bay high. Also seen on the second derivative map is anunclosed low forming directly west of Mount Adagdak in the general vicinity of the AndrewBay Hot Springs.

Microearthquakes I

From 22 October through 1 November 1974, more than 1000 km2 were surveyed nearAdak Island for microearthquakes. The objective was to detect and locate microearthquakesand thereby map tectonically active structures. Butler and Keller (1975, Reference 15) reportedon the results that would apply to the evaluation of geothermal potential at Adak.

The Aleutian Are is an active seismic province, with a large number of earthquakesoccurring on or near the subduction or Benioff Zone of the islands' arc-trench system (see

15

- - ~ ~ - * ~ '-..P

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BERING ",

I / .M7 ADAGD K

SANDREW 110

IcaIN

Scal e

FIGURE 5. Observed Aeromagnetic Map of Northern Adak Island. Contour interval 50 gammas(from Keller et al, 1954).

Engdahl, 1975; Reference 16). In the Aleutian Islands, the North Pacific Plate is postulated asbeing moved in a northwesterly direction as it is subducted under the American Plate. Thissubduction zone strikes east-west south of Adak and dips northerly to a depth of 100 to 150 kmbeneath the island. Although the seismic activity associated with the seismic zone is too deep tobe of interest in a microseismic survey, it is possible that the tectonic activity at depth isevidence of regional stress and that the stress pattern may influence surface faulting, withresultant seismicity.

16

4. C - . rlt ,

_____ __ .~1400-

NWC TP 6676

BERING SEA MT. ADA GD

ANDPEW 0 0

0t0 "N

FIGURE 6. Second Vertical Derivative Map of Northern Adak Island. Contour interval 100gaain0as/(0.5 mile) (from Keller et al. 1954).

Results from the survey indicated a seismically active zone near Andrew Bay striking: through Mount Adagdak. Butler and Keller interpreted it to be a right-lateral, strike-slip fault: with a small component of thrust (Reference 15). Allowing for uncertainties in the depth! parameter from the velocity model they were using, Butler and Keller fitted a fault plane

!0

striking N60°E and dipping 70°NW (Figure 7). They also hypothesized the existence of afractured or dilated region caused by this fault zone, located southwest of Mount Adagdak(centered along the spit north of Andrew Lagoon) and northeast of Mount Adagdak.

17

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"""", .- *""% ,,% , ; ."•"." . "0 0" 0."-" . ,"."h"." " r ,' . . o ", ' ,. . .'42'.:..'.;5 -"

NWC TP 6676

CAu

CIO

0

S-1

*cis

18~

NWC TP 6676

Electrical Surveys I

Butler and Keller also reported on a resistivity survey carried out on Adak by the ColoradoSchool of Mines in the fall of 1974 (Reference 15)., The survey used the rotating dipoletechnique along the southwest flanks of Mount Adagdak. Because of weather conditions,relatively few measurements were made before the survey was terminated. Results show a highresistive layer close to the source and then decreasing with depth (Figure 8). At distancesgreater than 1 km the apparent resistivity values decrease to less than 20 ohm-meters. Theselow valves are compatible with geothermal fluids at depth.

*N$ Adagdak

C, J-

"23 2nd

LOW

0 ~ mies _,

FIGURE 8. Apparent Resistivities Measured on Mount Adagdak in 1974 (modifiedfrom Butler and Keller, 1975).

19

K

NWC TP 6676

Electrical Surveys II

With the above information in hand, NWC tasked the United States Geological Survey(USGS) to explore Adak Island for a geothermal resource using various geophysical techniques.The studies were carried out in July and August of 1976 and included, among other things, theuse of audio-magnetotelluric, telluric, Geonics EM-16R, and self-potential electrical surveys.Unlike the survey performed by the Colorado School of Mines, these electrical studies usednatural instead of induced signals. Hoover (Reference 17), in a preliminary report referred toas the Hoover report, described the results paraphrased as follows:

co¢ Mount

Adagdak

0 I 2

miles

FIGURE 9. Telluric Map, Mount Adagdak (modified from Hoover, 1976).

20

C*..-.- --

SS S lop,

~-'~ ~ 'W~

NWC TP 6676

Magnetotellurics. Preliminary results from this survey suggest that the northern portion ofAdak Island has considerably more electrical conducting properties than the southern part. Thechange in intensity of the electric field variations, from Teardrop Lake (approximately 10 km

or 6.2 miles south of Finger Bay) to the southwest of Mount Adagdak, is approximately 25:1.This implies a 625:1 change in resistivity. The polarization of these currents on the northernportion of the island is indicative of the presence of a northeasterly trending conductor in thisregion (especially near Mount Adagdak). The persistence of the polarization of currents in anortheasterly direction, using periods of up to 1,000 seconds, suggested to the USGS that theconductor is sizable.

Tellurics. Seven telluric traverses were attempted on the southwest flanks of MountAdagdak; six of the traverses were parallel to each other in a N42°W direction; the seventh wasorthogonal to the others.

The telluric voltage map is shown by Figure 9, using the six parallel lines for information.The small closed low on the southeast end of traverse 1 is in an area with a number ofbuildings and may represent buried conductors. However, a northeast trend is apparent in thedata. The USGS feels this reflects the principal structural trends on the island. It suspects thata broad conductor exists beneath that part of Adagdak surveyed and that resistivity contrasts ofabout 100 to 1 are present between the edges of the volcano and the most conductive region inthe center. Since the low resistivity anomaly has a short wavelength, it is probably shallow.The USGS concludes that this could be a fault zone that has channeled thermal solutionsnearer to the surface.

Geonics EM-16R. This technique uses very low frequency radio transmitting stations foran energy source and directly measures ground resistivity in the frequency range of 15 to25 Khz. The survey was taken in conjunction with the telluric traverses and was useful inhelping to determine the upper value of resistivity on the audio-magnetotelluric soundings.Plotted values for this survey are shown on Figure 10.

Audio-magnetotelluric. This technique uses the orthogonal horizontal electric andmagnetic fields caused by worldwide lightning storms. Measurements are made from a range offrequencies from 7.5 to 18,000 Hz, with the lower frequencies giving greater depthpenetration.

Using the data gathered in the audio-magnetoteiluric survey, one-dimensional models werecomputed. Although these models are considered only approximate, a very good conductor onthe order of 1 ohm-meter was identified at a depth as shallow as 602 m.

Self-potential. Figure 11 shows the location and information gathered (in millivolts (my))from the self-potential (SP) survey done by the USGS on Mount Adagdak. Extremely large SPvoltages are noted on the north part of the island along with large voltage gradients. However,these voltages are thought to be due to the topography effect characteristic of an SP surveyperformed in mountainous areas (Mount Adagdak in this case) and not to any geothermalsystem.

The USGS did locate what appeared to be a long wavelength anomaly in the area ofMount Adagdak. It discovered this possible anomaly by running a line northwest along the spit

21

NWC TP 6676

C3~Adogdok

4.

I 2

miles

FIGURE 10. Apparent Resistivities Measured at 24 kHz (modified from Hoover, 1976).

between Andrew Lake and the Bering Sea. This traverse is nearly radial to Mount Adagdak,with less than 5 m variation along the line. The original intent of the line was to see if anyexpression of the fault identified by Butler and Keller (Reference 15) could be detected by usingthe SP method. The fault was not detected, either because the amplitude of the feature was toosmall or because the structure was farther west than the line extended. However, when the linewas extended to the northeast, up the slope of Adagdak, four other data points were obtainedwhere the line crossed previous traverses. There, the USGS detected a 200-mv anomaly ofunsymmetrical shape. The USGS is quick to point out that these four points are at a higherelevation than the 'spit' line and that some topographic correction should be applied. However,the correction would only increase the amplitude of the long wavelength to perhaps 400 mvand reduce the asymmetry. The USGS concludes that while the SP data are very speculative,they do suggest a large, deep source below the center of Mount Adagdak with the correctsignature for a geothermal system.

22

% - -

NWC TP 6676

.. , ,*,t2

.,,.-m ' * - "" Mount,;-2-

- Adagdak-1230 -Ia I

0- -so

F]GURE1 9-4. Sl-tetaVausMonAdda(mifd rM ount 17) Vle

40s3 0do71o

112 -33

in millivolts.

Gravity I

The data obtained from 30 gravity stations established on the northern part of Adak were

reported in the Hoover report. Elevation accuracies of the stations were considered to be

within 1.5 m with the exception of one station. The survey used the Adak Base Station at the

Naval Air Station as a reference for elevation control. Terrain corrections were made to a

distance of 2.6 kmn. The Bouguer anomaly values are posted and contoured on Figure 12.

Figure 12 shows that the gravity decreases to the north at about 2 milligas' (regals) per

kmn. Near Mount Adagdak and to the south a local gravity low and perhaps a smaller gravity

*A unit of acceleration used with gravity measurements; 10-s gal = 10- a ras.

23

NWC TP 6676

goum , IMOUNTm e

Xsg s t t

body evdene iGURi e 12ait Bopr Aomably Map Northaer Aa s aivnd, 1976. th no aou

Saeaay represet a lowi dnic tyone asocated wlith hote or perapsotea an c. arso

Temi

(Reernc 17):21

"Te raiy at idcaesalagemasoflo enit rc blo dada. h gavt

body~~~IGR evdece inue thAraiyorsmably isp thersaer ma sivng, rie9oth7 noaou.

dreay repreeat a seismni y ttone occated erwline Lake on Mounpsoteadan cmarso

Th fllwigisanexertfrm hesmmryasprsntd n heHovr24pr

NWC TP 6676

to other seismic stations on Adak - Personal communication to the USGS by R. Engdahl(1976)). The gravity also shows it is not at great depth although additional data is desired tobetter define the body.

"The MT data indicate again a large body and one with a northeast trend under Adak.The change in conductivity from the south part of the island to Adagdak is very large. If oneassumes a bulk resistivity in the south of 500 to 1000 ohm-meters, a value probably too high,then a large zone of 1 to 2 ohm-meters underlies Adagdak. These values are quite low anddefinitely indicative of a geothermal source.

"The telluric survey at 20-30 second period defines the southern part of Adagdak as beinganomalously conductive and defines a limited area to the northwest of the CommunicationsStation where conductive rock is nearest to the surface. The 100 to 1 range in conductivityfrom the edge of Adagdak to the anomalous center zone also suggests very low resistivities inthe area.

"The EM-16R and AMT surveys show the resistivity under Adagdak decreasing withdepth. The lowest values being in the area defined by the telluric survey and that a veryconductive zone is located there at about 600 meters in depth.

"The self potential data although quite speculative due to large noise voltages also can beinterpreted as suggesting a large anomalous body below Adagdak at depths of about 2 to 3kilometers.

"These geophysical data show that a low density, very conductive, mass of rock underliesMt. Adagdak, that its top is quite near the surface, and that it is probably elongated in anortheast direction. The low values of resistivity also imply hot or molten rock. Additionalwork is definitely indicated to further identify this probable geothermal system."

OBSERVATION HOLE DRILLING

The Navy used the results ot the Hoover report and previous studies to site two slim drillholes. Results of the drilling are as follows:

Two observation (stratigraphic) holes were drilled as shown in Figure 13. The drilling wasdone in the summer of 1977 by the Hamilton Drilling Company, which used a track-mountedLongyear drilling rig. Hamilton intended to core; however, the large amounts of clayalteration dictated rotary drilling. Both holes were completed with 2-inch capped black ironpipe cemented in and filled with water.

Hole 1 was sited by the USGS on the basis of its geophysical studies. It was drilled to995 ft on the southwestern flanks of Mount Adagdak. Much to the surprise of the NWC andUSGS personnel, the entire hole was drilled in volcanic ash altered to montmorillonite withoccasional volcanic boulders or flows. A maximum recording thermometer lowered to thebottom of the hole on 12 January 1978, and left there for 2.25 hours, gave a reading of 75*F.Using a mean air temperature of 40*F (Reference 1, p. 376) would give an overall thermalgradient of 3.5'F/100 ft (6.4'C/100 m).

25

NWC TP 6676

60

Andr ewN

Lo Lagoon

contour intervol 101) meters

FIGURE 13. Locations of Observation Hole 1 andObservation Hole 2.

The second hole was located by NWC by projecting the trend of the most prominent jointpattern at the Andrew Bay Hot Springs into the geochemical and geophysical anomalies. Thehole was also located along a road for environmental reasons. It was drilled to a depth of1,925 ft, through competent but fractured rock.

A temperature log on this hole is shown as Figure 14. Detailed lata are contained inAppendix C. The gradients (from 50 to 1,925 ft) of 4.2°F/100 ft (7.6°C/100 m) are notspectacular but are encouraging. The gradient curve is a straight line, indicating conductiveheat transfer. Extrapolating the curve would indicate that a temperature of 190°C would beattained at a depth of about 4,000 ft.

ADDITIONAL GEOPHYSICAL SURVEYS

In the summer of 1982 NWC conducted additional gravity and magnetic surveys; made areconnaissance soil survey of mercury content; and contracted with the Earth SciencesLaboratory, University of Utah Research Institute. for a microseismic survey. All of the surveyswere confined to the northern part of the island.

26

1- , .Y'y. Z>

NWC TP 6676

TEMPERATURE (F*)45 60 75 90 105 120

0

100 ',

200

\ Observation Hole 2300 \ - o0 in TD 1925ft.

",\\ .... log out '

400

500

600

700

800

900U-

'1000I- Observation Holea.Uj 100 T D

= 995 ft.C

1200

1300

1400

1500

1600.

1700

1800

1900

2000 Logged 10-24-78, R. Clodt, J Neffew

FIGURE 14. Graph of Temperature Log From ObservationHole 1 and Observation Hole 2. Graph of Observation HoleI based on single point at total depth (T.D.)

Gravity II

A total of 301 gravity and land magnetic stations were occupied in July and August 1982.Fifty-three stations were taken at existing bench marks on the island, and 248 by-stations werecreated using a Wild T-1 theodolite and two wide-faced rods. Surveying of the new stationstook place despite unfavorable weather of torrents of rain alternating with gale-force winds;elevation accuracies were better than 0.4 ft. Gravity was measured at each station by aLaCoste and Romberg gravity meter (Model G-144), in a series of 4-hour drifts withcheckpoints, and tied to the Adak Base Station. The findings were then reduced with thepost-1967 latitude correction (Reference 18), assuming a reduction density of 2.67 gm/cc.Terrain corrections were taken in the field to a distance of 175 ft (Zone C of a Hammer chart

27

• . -:K. :-. . d. .'. .° ..;.' . - .' . " " . . " . " ... .. ; " .'. , r r'r ,,' ' ' ' - ' -. -

NWC TP 6676

in Reference 19), manually with a map through about 8,600 ft (Zone H of a Hammer chart).

and then with a computer through approximately 72,000 ft (Zone M).

Figure 15 shows the Navy's gravity survey, plotted using a reduction density of 2.67 gm/ccand contoured on an interval of 1 mgal. Comparison of Figure 15 with the gravity surveyreported by Hoover (Figure 12) does not show any great dissimilarity. The northward decreaseof the Bouguer anomaly values appears the same, although the large gravity gradient south ofMount Adagdak shows slight tightening. It is not known how far north the decrease extends,however, because the Navy's survey did not include any points on the flanks of Adagdak due tothe lack of survey time and bad weather. The Navy's survey did delineate the localized highnear the Andrew Bay Hot Springs as seen by the USGS.

-1

NMiles

I -- I

I 220-II

I

FIGURE 15. Bouguer Anomaly Map, NorthernAdak Island, 1982. Contour interval, 1 mgal;reduction density, 2.67 gm/cc.

28

NWC TP 6676

The Navy defined two localized lows in the vicinity of the Adak airfield. This findingcorresponds well to the outcrops of andesite porphyry domes as mapped by Coats, andprobably indicates that that rock type also exists at a shallow depth beneath the airfield(Reference 3).

A simple regional gravity trend was subtracted from the complete Bouguer gravity toreveal the residual gravity. The regional trend assumed a constant 2 mgal per mile decreasenorthward across the island. This regional gravity trend was discussed by Hoover and wasbased on information provided by Grow (References 17 and 20). A trend of N60*E wasdetermined for the regional since this is the predominant structural trend on the islands of theAndreanof group (Reference 3).

The residual gravity map is shown in Figure 16. The predominant feature of the map isthe northeast gravity trend that passes through both Andrew Lagoon and Clam Lagoon. Cross

-9

>N

FIGURE 16. Residual Gravity Map of NorthernAdak Island. Map constructed by subtractingfrom Figure 15 regional gravity gradient of 2mgals/kn trending N60 0E.

29

" "% " " • " ' ." % ," " - " " " " " "' . - - " " " N. ,'; " " \ .¢ . : " " . . . .¢ " " " " " ' " " " : " Z " " ', -: " r " "

NWC TP 6676

section A-A' was drawn across the feature to attempt modeling. Using the fact thatObservation Hole 1 drilled through almost 1,000 ft of clay, and that the two microseismicsurveys delineated a fault structure dipping at nearly 70 degrees to the north, the feature wasmodeled as a fault assuming a density contrast of 0.4 gm/cc (2.2 gm/cc for the clay; 2.6 gm/ccfor the Finger Bay volcanics). Results of the modeling are shown in Figure 17. This figureshows that the feature resembles a dip-slip fault with a throw of nearly 2,800 ft. The excessmass near the center of the fault model could represent a slide-block formed during faulting.The residual map of Figure 16 also clearly shows the gravity high found near the Andrew BayHot Springs.

FAULT MODEL 1312

2800 PP- 2.9gqm/cc 1

P' 2.5 gm/ce 9

8

7_r

6-

5 r(n

4

3

o RESIDUAL PROFILE 2

0 COMPUTE[, PROFILE

A| 2 .1 0 12 1 4 16 A

"MOU,ANDS Or F FT

FIGURE 17. Simple Fault Model Along Section A-A' on ResidualMap (Figure 16). Calculations based on formula from Geldart et al,1966 (Reference 21).

Land Magnetics

Land magnetics were taken with a Geometries magnetometer in conjunction with thegravity survey. No recording base station was used. The data were smoothed by repetitiverecording from base stations and checkpoints. Appendix D contains all data on the Navy'sgravity and land magnetic studies.

Figure 18 shows the results of t: land magnetic survey. There was some difficulty ingathering the magnetic data because of the enormous amount of buried ferrous material leftfrom World War II and later. To counter this effect, numerous stations were occupied morethan once during the course of the survey. The data were then smoothed by using thesecheckpoints. Data that were obviously affected by possible buried material were deleted. Thedata were then plotted and contoured on an interval of 500 gammas.

30

.- *-

NWC TP 6676

4

L

4848 48

49I 4

I 48

47 H

48 4

0' I

pie

49

FIGURE 18. Ground Magnetic Map of NorthernAdak Island. Contour interval in gammas. Allvalues times 1,000. H = magnetic high anomaly;L - magnetic low anomaly.

The most prominent features shown by the magnetic survey are the localized highs locatednear the airfield. These highs correlate well with the outcrops of andesite porphyry domesdiscussed in conjunction with the gravity survey, and they are probably the magnetic signatureof the accessory magnetite that Coats describes within the groundmass of the porphyry(Reference 3). Another high exists at the site of the old airfield south of Mount Adagdak, but itis not certain whether this high is due to the existence of a buried andesitic dome or themagnetic expression of near surface metal artifacts. Other prominent features indicated are thefaint outlines or suggestion of magnetic highs within Clam Lagoon and Andrew Bay, as well asan emerging low on the western flanks of Mount Adagdak.

31

NWC TP 6676

SOIL GEOCHEMISTRY

Soil sampling was conducted to determine mercury content; mercury often occurs inunusually high amounts in soils over geothermal resources.* A reconnaissance soil survey wasrun on the northern end of Adak Island. The writers knew of no references to soil geochemistryin tundra and had reservations as to its effectiveness, as Hoover had reported high resistivitiesin the surface layer of soil on Adak because of excessive leaching (Reference 17). Samples werecollected from the base of the surface vegetation, if present, or just below the surface ifvegetation was not present. A plastic scoop was used to collect samples, which were placed inplastic zip-lock sandwich bags. The samples were then flown to NWC and analyzed with aJerome mercury detector. The samples did contain significant amounts of mercury; data and

locations are given in Appendix E. Soil types were classified as gravelly, sandy, ashy, andmucky (highly organic). Mean mercury content together with standard deviations is given inTable 3.

TABLE 3. Mean Content of Mercury by Soil Type,Geochemical Samples, Northern Adak Island, Alaska.

Soil No. Mean mercury Standard deviation,type samples content, ppb a ppb

Gravelly 6 30.2 11.63Sandy 16 41.0 34.40Ashy 6 46.8 40.85Clayey 35 69.0 40.98Mucky 11 87.27 40.98

a ppb = parts per billion.

From the Table 3 entry for mucky soils, it can be seen that organic matter is an importantfactor in fixing mercury in soils in subarctic climates.

A histogram of frequency of soil mercury contents is given as Figure 19. Contouredmercury contents are shown as Figure 20. Because of the low number of samples, contouringwas done independently of soil type. Each anomaly contained several soil types. Therefore,although the contours would be somewhat different if sample size had been large enough tocontour by soil type, the same pattern of high values and low values would exist.

Many of the observed anomalies correlate to those found by the gravity and groundmagnetic surveys. The low mercury anomalies at the airfield and at the communicationsstation are probably the signature of buried or partially buried andesite porphyry domes. Theanomaly at the mouth of Clam Lagoon directly west of Zeto Point is probabiy also a surfaceexpression of a buried andesite porphyry dome, although it is not clearly shown by thegeophysics. The high mercury anomalies directly west and south of the airfield lie in thehighlands and are likely to represent volcanic rock of the Finger Bay formation. The highlocated on the western flanks of Mount Adagdak may also represent the interbedded lava flowsas mapped by Coats and reported in Reference 3. However, the drilling that was done in thisarea indicated that over 1,000 ft of altered volcanic material is present. This signature thencould be the surface expression of geothermal alteration of volcanic rock into clay. Themigration of geothermal fluids tends to concentrate mercury directly above the fluid path.

Mercury in soil is what is known as a "pathfinder element" for base metal deposits and epithermal (low.temperature) gold and silver deposits, as well as geothermal resources.

32

~ -N'

NWC TP 6676

_. _.xll lx

< 1

C

00

o "

-I P

0 2 0 60 0 I00 2 4 6 0

0

Poto/ious 6hFoncentrotions 5 3

4.

3

0 20 40 60 80 100 120 140 160 180 200

Parts/ Billion

FIGURE 19. Frequency Distribution of Mercury Content in Soil Samples, Northern Adak Island.

A rock sample taken 200 ft above the Andrew Bay Hot Springs contained 283 ppbmercury. A rock sample from the spring itself gave a mercury content of 54 ppb.

Three samples were taken in the vicinity of the Kiguga Warm Springs. Sample 1, takenfrom just beneath the tundra, had a mercury content of 39 ppb, well within the backgroundrange. Sample 2, taken directly from the area of seepage at the silicified zone, had anextremely anomalous mercury content of 1,582 ppb. The third sample, taken from 30 yards tothe south in an iron-stained silicified zone, had a mercury content of 316 ppb. Again, this is ananomalous sample. The type of alteration (sericitization and silicification, the introduction ofpyrite, and the extent of alteration) makes the Kiguga Warm Springs area an attractiveexploration target. The location, however, would present logistic problems both from thestandpoint of exploration and utilization.

For selected samples, qualitative scans were run using a Kevex 0700 Energy DispersiveX-ray Spectrometer to check for heavy metals. If metals were present, the unit was used tocheck possible positive or negative correlations with the mercury content. Screened soil sampleswere placed in cups, covered with Mylar, then scanned. Because of interferences, only thefollowing elements could be checked: silver plus indium, manganese, copper, and zinc. Countsper fixed time gave low correlation coefficients against mercury when fitted by least squares tolinear, logarithmic, power, ana exponential curves.

Surprisingly, no arsenic or antimony was found in any sample. These elements aregenerally indicative of shallow recent geotherma' or epithermal fluid-migration zones.

33

K - , ' -: % ' j .- :. "; '-i='.:. -v , ,': - * , r- , y • "w r - w - -

NWC TP 6676

0-

30 50100

CLAM LAGOON70

I IN

Miles)O~ /

150 30 ZETO POINT

0120

50

FIGURE 20. Contoured MercuryConcentrations in Soil Samples,Northern Adak Island. Contour intervalin parts per billion.

MICROEARn rlQUAKES II

During 1982 NWC contracted with the Earth Science Laboratory, University of UtahResearch Institute to perform a microearthquake survey of northern Adak. The survey wasmeant to substantiate the seismicity survey of the same area by Butler and Keller (Reference15). The survey, undertaken in early fall, recorded 190 discrete seismic events, of which 33were determined to be of local origin. Of these seismic events, 24 were located. The eventswere analyzed when recorded on two or more stations of a nine-station network. Results werereported by Lange and Avramenko (Reference 22).

The hypocenters of the located events delineated a fault plane dipping north-northwestbeneath Mount Adagdak toward the Bering Sea (Figure 21). The surface projection of the faultappeared to pass through Clam Lagoon. However, these determinations were made assuming a5 km/s constant-velocity earth model and would probably change if a more realistic earthmodel were used. The survey does support the north-northwest-dipping fault plane deducedfrom the 1974 survey except for the fact that the trace lies north-n, west of the one locatedin a later survey (References 15 and 22).

34

wt" - :. J_. . - -. f:-

NWC TP 6676

-A

010

00

00,

w-

cq~X

0 L0

U,

wa

0 <'

L %I. Z 7x )0000 I 0-1'

35

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AERIAL PHOTOGRAPHY INTERPRETATION

A study of the northern part of Adak Island by means of high-quality ae-ial photography(scale 1:76000) was attempted to delineate any faults or lineations. While much of thestructure appears to be obliterated by the presence of the volcanoes, some interesting featuresdid present themselves. Results of the study are shown by Figure 22.

The most obvious feature on the aerial photographs is an east-west-trending fault thatpasses south of Mount Moffett and traverses the Naval Air Station just north of the airfield("A", Figure 22). Since the trace of the fault cuts through flows from Mount Moffett andapparently shows some movement (probably south side up, strike movement not determinable)this may have been the fault that Professor Bruce Marsh was looking for during a study in 1981of airfield runway cracks on the north runway (Reference 23). Marsh states that, during astudy in 1973, it was found that significant inundation had occurred during earthquakes alongthe beach just north of the southern two andesitic porphyry domes (Figure 23). AlthoughMarsh assumed a northeast-trending fault with right lateral offset to explain the separation ofthe southern two domes from the northern three, he concluded after a study in the area of thesouthern domes and of the runway that no significant fault could be found. However, the faultfound on the aerial photographs passes directly through the area of inundation and couldpossibly be active.

NMiles1 0 .

Lineations-Obvious

I t---FeintI -_ - " . _ _.-P-.Questionable

/

I ./

FIGURE 22. Map Indicating LineationsDeduced From High-Quality AirPhotographs of Northern Adak Island.

36

r--~. ri''~rr 7- r7--. I~ .t r -.X -

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Andrew Bay Mount

Hot Springs dagdak

MountMof fett

1. inundated duringearthquake activity

I. (Marsh, 1981)'

0 5 10 15 20

MILES

FIGURE 23. Map of Adak Island Indicating Possible en Echelon Faulting on a Strike of N600E.

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NWC TP 6676

Another fault that was located by examination of the aerial photographs is a north-south-trending fault that cuts Mount Adagdak. It can be traced from Cape Adagdak south, passingdirectly east of the largest basalt/andesite dome on Mount Adagdak, through Clam Lagoon,where it probably is responsible for the existence of the small "island" within the lagoon, andthen on out into Kuluk Bay. If the trace is extended far enough to the south, it passes throughThumb Bay just east of Finger Bay. The fault is probably slightly east side up, but any strikemovement is unknown.

Other obvious faults as seen on the aerial photographs are those on the hill betweenAndrew and Clam Lagoons. These were mapped by Coats (1956, Reference 3) and others.

Figure 22 also indicates the locations of faint lineations indicated by the photos. Althoughcut by the faults previously mentioned, a great number of the lineations strike northeast andparallel the trend of the Finger Bay Fault. Other lineations strike due east-west while a thirdset near the communications station strikes northwest.

OTHER OBSERVATIONS

The Finger Bay Fault is one of the most pronounced structural features on the island. It istraceable on the large-scale topographic maps from Lucky Point west through the Bay ofIslands and into the North Arm of Three Arm Bay (Figure 23). As a mental exercise, considerthe possibility of "pushing" the islands within the Bay of Islands, along with the main mass ofnorthern Adak, 3 miles along the Finger Bay Fault trace and up against Argonne Point. Inessence, the Bay of Islands would close up, in a closing similar to that of oceans in the theoryof continental drift. The Finger Bay Fault, which strikes in a N60°E direction, would thenhave at least 3 miles of right lateral movement. This distance, coincidentally, is the same rightlateral distance when drawn on a line of N601E between the two southern and three northernandesitic domes on Kuluk Bay and could represent the fault that Professor Marsh thoughtactive. The direction N60°E also defines the line drawn from the large volcanic vent on MountAdagdak, through the Andrew Bay Hot Springs, and then through the large vents on MountMoffett. It appears possible that the entire northern half of Adak Island once moved, orcontinues to move, in a series of right lateral, en echelon faults, all striking N60*E (Figure 23).One of these faults may have defined a large zone of weakness, where the nagmatic fluidswere emitted. This zone may now emit geothermal fluids, even though it could be broken upby faults of different strike.

SUMMARY AND DISCUSSION

The northern half of Adak Island appears to contain the only surface evidence of activegeothermal potential at depth. This evidence is manifested in hot springs located on the shoresof Andrew Bay and warm springs located on the west side of Mount Moffett. Other evidence of

% past activity on the island is the occurrence of three volcanoes on the northern part of theisland (Mounts Moffett and Adagdak and the Andrew Bay Volcano).

*: The vents of the volcanoes and the hot springs lie along a lineation or fault that strikesapproximately N60°E. Fraser and Snyder studied maps and photographs and found thelineations of the southern half of Adak Island are strongest to the northeast (Reference 1).

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NWC TP 6676

Joints measured in southern Adak that strike northeast are vertical or dip steeply to thenorthwest. N60°E corresponds closely to the predominant direction that Coats found on otherislands located within the Andreanof group lying to the east of Adak (Reference 3). This trendalso coincides with the direction of the Finger Bay Fault, where there is some evidence ofcertain sections of the fault having a right lateral movement of nearly 3 miles. Indeed, Fraserand Snyder suggested that the Finger Bay Fault and the major Adak fault of Bradley wereinstrumental in blocking out or segmenting the islands (References 1 and 2 respectively).

Results of two microseismic studies 8 years apart indicated that a fault trendingapproximately N60°E and dipping more or less 70 degrees to the northwest was present, eithercutting through Mount Adagdak or directly south of the mountain. Results of two gravitysurveys tend to confirm this interpretation. Using information from a drill hole as a parameter,modeling of the gravity information indicated that the fault may be down-dropped to thenorth by as much as 2,800 ft. However, field work attempted by Marsh (1981) and Brophy(1982) did not uncover any surface evidence of the existence of the fault, nor did aerial-photograph analysis by a number of investigators (although the authors in their analysis diddiscern faults trending east-west and north-south in that area) (References 23 and 13).

The Andrew Bay Hot Springs lie on the southern flanks of an unclosed gravity highdiscerned by the two separate surveys. Directly east and south of the high lies a large gravitylow. This low, coupled with the results of numerous electrical surveys, led the USGS to surmisethat the subsurface of Mount Adagdak could be hot or perhaps molten at a shallow depth.Guided by the USGS theory and expecting a few feet of tundra and volcanic ash followed bycompetent rock, NWC drilled a slim hole at a site preselected by the USGS. To the surprise ofeveryone, the hole contained nearly 1,000 ft of altered volcanic ash in the form of clay. Sincethe drill hole lies in the trend of a fault inferred by numerous surveys, it seems possible thatcirculating hot geothermal fluids have altered all rocks within the fault plane into clays. Thisgeothermal alteration would account for the low-density rock seen by the gravity surveys andthe highly conductive rock measured by the electrical studies. The thermal gradient measuredin the drill hole was 3.5*F/100 ft.

A second drill hole was located north of the first, approximately three-quarters of a mileeast of the Andrew Bay Hot Springs and into the flanks of the gravity high. The hole wasdrilled to a depth of 1,925 ft, and competent but fractured rock was encountered throughoutthe entire depth. The thermal gradient of this hole measured 4.20 F/100 ft.

.he Andrew Bay Hot Springs are almost 200 ft apart on the east side of Andrew Bay andhave measured temperatures in excess of 158'F. Water samples taken from the springs areessentially brines, probably because of an oceanic water component. The total of dissolvedsolids in the Andrew Bay Hot Springs is about two-thirds that of oceanic brines. However, thesprings do contain a high concentration of silica and boron along with high values ofbicarbonate and calcium. Miller and Smith suggest that the high concentrations of bicarbonateani calcium are due to the leaching of volcanic rocks (Appendix A). The fact that the springsalso have a high silica content may indicate that the gravity high detected near the hot springsmay bo, due to silica deposition within the near-surface rock. If this is the case, the gravity highwould b the next logical target to drill since it may represent the cap rock ovei tlhe geothermalreservoir.

Supporting +he above interpretation is the occurrence of an unclosed aeromagnetic lowseen on the second derivative map in this area. If the gravity high does indicate the deposition

39

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of silica material by geothermal fluids, then this aeromagnetic low may indicate thepyritization of magnetite minerals by those same fluids. A magnetic low is also seen on the

ground magnetic map in this area and may indicate the same phenomenon. The high mercurycontent of soils on the western flanks of Mount Adagdak are a fourth likely indicator of near-surface geothermal fluids.

Geothermometry results indicate reservoir temperatures of 155 to 186 0C for the AndrewBay Hot Springs. Motyka calculated a deep reservoir temperature of 160 to 188*C. Motyka, ina personal 1985 communication to the authors, states that the hydrothermal system isinfluenced by magma. He determined this by use of helium ratios and analyses of 13C infumarolic CO2.

The Cape Kiguga Warm Springs are located on the beach, 1 mile south of Cape Kiguga.Measured temperature at these springs was 60'F, and they had a pH of 4.5 (Reference 4).Iron-mineral depository springs were seen along the margins of the main spring area andextended southerly along the beach for about 1 mile. Brophy also visited the warm springs andthought that, because of the degree and extent of alteration and silicification, the springs mayhave been a former major hot spring system (Reference 13). He thought that they had beenlarger, at one time, than the Andrew Bay Hot Springs currently are. Since no geophysical workwas done in the vicinity of the Cape Kiguga Warm Springs, it is not known what type ofgeophysical signatures, if any, might characterize the area. Mixing models gives the KigugaWarm Springs a deep reservoir temperature of 54 to 91'C.

Elsewhere on northern Adak Island, the andesitic porphyry domes are characterized bylow gravity, low mercury, and high magnetic anomalies. These geophysical anomalies arelocated along Kuluk Bay, in good agreement with the domes mapped by Coats in Reference 3.This rock type probably underlies the Naval Air Station facilities more extensively thanpreviously thought. The ground magnetics and mercury studies indicate that another domemay underlie the communications station. The gravity signature of this dome is apparentlymasked by the lower density subsurface rocks, as it is not delineated on the gravity surveys.

CONCLUSION

Proof of an economic geothermal resource on Adak Island can be verified only by furtherdrilling and actual production. The geological, geophysical, and geochemical data clearlyindicate that a geothermal prospect worthy of drilling exploration is present on the northernpart of Adak. The data also indicate that the western flank of Mount Adagdak, near the shoresof Andrew Bay, has the highest potential for developing a geothermal resource at modestdepths. This site presents a favorable drilling target that should be tested by drilling to a depthof not less than 4,000 ft; a depth of 6,000 ft would be considered optimal.

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REFERENCES

1. G. D. Fraser and G. L. Snyder. "Geology of Southern Adak Island and Kagalaska Island,Alaska," USGS Bull. 1028-M (1959), pp. 371-408.

2. C. C. Bradley. "Geologic Notes on Adak Island and the Aleutian Chain, Alaska," Am.]our. Sci., Vol. 246, No.4 (1948), pp. 214-40.

3. R. R. Coats. "Geology of Northern Adak Island, Alaska," USGS Bull. 1028-C (1956),pp. 45-67.

4. J. L. Moore. Adak Geological Investigations; draft of trip report. California EnergyCompany, Inc., Santa Rosa, Calif. 1981.

5. Robert 0. Fournier. "Application of Water Geochemistry to Geothermal Exploration andReservoir Engineering," in Geothermal Systems: Principles and Case Histories, ed. byL. Ryback and L. J. P. Muffler. Chichester, England, John Wiley & Sons Ltd., 1981.Pp. 109-43.

6. A. H. Truesdell. "Geochemical Techniques in Exploration," in 2nd Proceedings, U. N.Symposium on the Development and Uses of Geothermal Resources, San Francisco, 1975.Vol. 1 (1976), pp. liii-lxii.

7. R. 0. Fournier and A. H. Truesdell. "An Empirical Na-K-Ca Geothermometer for NaturalWaters," G6ochimica et Cosmochimica Acta, Vol. 37 (1973), pp. 1255-75.

8. R. 0. Fournier and R. W. Potter II. "Magnesium Correction to the Na-K-Ca ChemicalGeothermometer," Geochimica et Cosmochimica Acta, Vol. 39 (1979), pp. 1543-50.

9. T. Paces. "A Systematic Deviation From the Na-K-Ca Geothermometer Below 75 'C. andAbove 10 -4 atm: PCO, " Geochimica et Cosmochimica Acta, Vol. 38 (1975), pp. 541-44.

10. R. J. Motyka. 'High- 2i'emperature Hydrothermal Resources in the Aleutian Arc," inProceedings, Alaska Geological Society Symposium on Western Alaska Geology andResource Potential, 1982. Pp. 87-99.

11. A. H. Truesdell and R. 0. Fournier. "Procedure for Estimating the Temperature of a Hot-Water Component in a Mixed Water by Using a Plot of Dissolved Silica VersusEnthalphy," 1. Res. U.S. Geol. Survey, Vol. 5, No. 1 (January-February 1979), pp. 49-52.

12. R. 0. Fournier. "Geochemical and Hydrologic Considerations and the Use of Enthalpy-Chloride Diagrams in the Prediction of Underground Conditions in Hot-Spring Systems,"I. Volcano. Geotherm. Res., Vol. 5 (1979), pp. 1-16.

13. J. G. Brophy. Summary of Geologic Field Work Conducted on Adak Island 7/28 to 8/6;informal report. Baltimore, Md., Johns Hopkins University, 1982.

14. F. Keller, -r., J. L. Meuschke, and L. R. Alldredge. "Aeromagnetic Surveys in theAleutian, Marshall, and Bermuda Islands," Trans. Amer. Geophys. Union, Vol. 35, No. 4f(1954), pp. 558-72.

15. D. L. Butler and G. V. Keller. Exploration of Adak Island, Alaska; Appendix B ofGeothermal Energy in the Pacific Region. Grose & Keller Naval Research ContractN00014-71-A-0430-0004, 1975.

16. E. R. Engdahl. Seismicity and Plate Subduction in the Central Aleutians, CooperativeInstitute for Research in Environmental Sciences, Univ. of Colorado/NOAA, 1975[?]

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17. D. B. Hoover. Geophysical Techniques Applied to the Evaluation of the GeothermalPotential of Adak Island, Alaska; preliminary USGS report (unpublished), 1976.

18. W. M. Telford, L. P. Geldart, R. E. Sheriff, and D. A. Keys. Applied Geophysics,Cambridge, Cambridge University Press, 1976. P. 15.

19. S. Hammer. "Terrain Corrections for Gravimeter Stations,"Geophysics, Vol. 4 (1939),pp. 184-94.

20. J. A. Grow. "Crustal and Upper Mantle Structure of the Central Aleutian Arc," Geol. Soc.Amer. Bull., Vol. 84 (1973), pp. 2169-92.

21. L. P. Geldart, D. E. Gill, and B. Sharma. "Gravity Anomalies of Two-DimensionalFaults," Geophysics, Vol. 31 (1966), pp. 372-99.

22. A. L. Lange and W. Avramenko. Adak Island, Alaska Microearthquake Survey:Preliminary Hypocenter Determinations, Subcontract for Earth Science Laboratory,University of Utah Research Institute, U.S. Dept. of Energy Contract No. DE-AC07-80ID12079, 1982.

23. B. D. Marsh. Field Work on Adak Island, Aleutian Islands, Alaska, July 29, 30, 31, 1981;informal report. Baltimore, Md., Johns Hopkins University, 1981.

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Appendix A

GEOLOGICAL TECHNIQUES APPLIED TOTHE EVALUATION OF THE GEOTHERMAL

POTENTIAL OF ADAK ISLAND. ALASKA

by

Thomas P. Miller and Robert L. SmithFebruary 8, 1977

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Introduction

The U.S. Navy contracted with the U.S. Geological Survey in early

1976 to make an evaluation of the geothermal resources available on

the naval station on northern Adak Island in the central Aleutian

Islands. The U.S.G.S. accordingly began work in the summer of 1976 witi

a two-phase program consisting of (1) a geologic study concentrating

on the petrology, chemistry, and geochronology of the recent volcanoes

in the immediate area and (2) a geophysical study. This part of the

report deals with the results of the geological investigations, most

of which were concentrated on Mount Adagdak because of the apparent

youthfulness of the volcano, Its stage of evolution, and Its access.

The field work was done by Dr. Thomas P. Miller and Robert L. Smith

during the period July 26-August 9, the geochronology studies were done

by Dr. G. Brent Dalrymple, and the chemical analyses were done under

the direction of Brent Fabbi, all of the Geological Survey.

Regional Geologic Setting

Adak Island is located in the central Aleutian Islands and Is

part of the Aleutian arc, a seismically active volcanic arc-trench

system that extends for more than 2000 km across the north Pacific.

Over 60 major volcanic centers of Quaternary age occur along the

northern edge of this arc and at least 40 of these have been active in

the past 200 years (Coats, 1952). The volcanism appears to be the

result of northward subduction of the Pacific plate beneath the North

American plate with magma bii.ng generated along the Benioff seismic

zone which lies some 100 to 125 km beneath Adak Island. The northern

44

**.. **. '.*.~ .. -** ~ ~ ** *.* **-' *** * ~ .. .*

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part of Adak Island contains three of these volcanic centers, Mt. Moffett,

Andrew Bay, and Mt. Adagdak.

Summary

Information obtained from a study of the petrology, age and

composition of the three volcanoes on the north side of Adak Island was

used in an attempt to determine whether thermal anomalies may be present

beneath the volcanoes. Of the three volcanoes, Mt. Adagdak appears to

have the highest probability for the existence of an underlying thermal

anomaly of significant size. Mt. Moffett has a lesser probability

and Andrew Bay volcano has a relatively small probability for a

thermal anomaly of any magnitude.

On the basis of geological studies alone, the geothermal potental

of northern Adak Island can be considered as marginal only. The

decision for further work, including drilling, should be based on an

integration of the geophysical and the geological data and a cost

analysis study of the benefits of relatively cheap geothermal energy

versus the costs of further exploration.

Local Geology

Most of Adak Island is underlain by the Finger Bay Volcanics, a

thick (at least 1500m ) series of predominantly pyroclastic rocks and

lava flows chiefly of basaltic and ande0.tic composition but including

minor amounts of rhyodacite. The unit is moderately deformed, inten-

sively altered, and was intruded by granodiorite plutons in Miocene

time (about 13-14 m.y., Marlow and others, 1973). The unit is con-

sidered to be early Tertiary in age and part of the "early series" of

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exposed rocks found i'n the central and western Aleutians (Marlow and

others, 1973).

The Finger Bay Volcanics are overlain by the Andrew Lake Formation,

a sequenceof marine sedimentary rocks more than 850 m thick and corn-

posed chiefly of tuffaceous sandstone, siltstone, and siliceous shale

interbedded with mafic flows. The unit was considered by Coats (1956)

to be Paleo~oic in age but more recent work by Scholl and others (1970)

has shown it to be of middle or late Eocene age. The Andrew Lake

Formation appears to rest depositionally on the Finger Bay Volcanics

and is best exposed along the eastern shore of Andrew Lake (fig. 1).

Scholl and others (1970) suggest that the unit was probably laid

down in a perched basin along the crest of an early Tertiary Aleutian

ridge; possible analogues exist in the present ridge system.

Several small glaciated domes crop out in the vicinity of Kuluk

Bay (i.e. Zeto Point). They are composed of hornblende andesite,

intrude both the Andrew Lake Formation and the Finger Bay Volcanics,

and have yieldedK-Ar ages of about 5 m.y. (Marlow and others, 1973).

Volcanic and volcaniclastic rocks associated with Mount Moffatt,

Andrew Bay, and Mount Adagdak volcanoes unconformably overlie the

Andrew Bay Formation. Mount Moffett and Mount Adagdak physiographi-

cally dominate the north part of Adak Island. Mount Moffett appears

to be a typical andesitic stratocone some 10 km in diameter and

composed of intercalated flows and tuffs with associated domes and

parasitic cones. Andrew Bay and Mount Adagdak volcanoes on the other

hand appear to be dominated more by large andesitic to dacitic domes

46

-- - - - . - . * -- . - - , - -- - -

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emplaced in central vents of andesitic stratocones considerably smaller

than Mount Moffett. All three volcanic centers have been assigned by

Marlow and others (1973) to the "late series" of exposed rocks In the

region and were considered to be of late Tertiary and Quaternary age.

There are no known accounts of historic volcanic activity (i.e. <200

yrs.) associated with these three volcanoes.

Most of northern Adak Island was covered by Pleistocene glaciers

which originated in the highlands in the southern part of the island

and lapped well up on the flanks of Mount Moffett and Mount Adagdak;

moraines from this glaciation have been found by Coats (1956) at

elevations of 500 feet on Mount Adagdak. Valley glaciers were formed

on Mount Moffett and appeared to head in cirques on the north and

northeast side of the volcano.

A well-stratified layer of volcanic ash, locally as much as

several feet thick, mantles much of the lower elevations of north

Adak Island. The ash is post-glacial and thought to have come from

volcanoes on nearby islands, particularly Kanaga and Great Sitkln.

The presence of pumice-rich layers in the ash suggests they may have

originated during the caldera-forming eruption of Kanaton caldera on

Kanaga Island.

Hot springs have long been known to occur along the east side

of Andrew Bay and were sampled during the course of this study.

Numerous steeply dipping normal faults of relatively small

displacement occur south of the volcanoes. These faults generally

strike N. 600 E. to N. 600 W. and from N. 200 E to N. 100 W. (Coats,

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1956); they do not cut the Quaternary volcanoes. Many of the faults

shown by Coats on Mt. Adagdak appear to represent landslide scarps

on the unstable north flank of the volcuno facing the ocean.

Geochronology

The three volcanoes on the north side of Adak Island were thought

by Coats (1956) to be late Tertiary to perhaps late Quaternary in age.

based on morphology and similarity to other volcanoes in the arc.

Cameron and Stone (1970) reported K-Ar age measurements of 0.0±0.16

m.y. and 0.0±0.23 m.y. for fresh olivine basalt collected from basal

members of Mount Adagdak volcano along the southeast sea coast. They

state that it is highly unlikely that the sample could be older than

500,000 yrs.

Marsh (1976) in a recent paper on Aleutian andesites reported a

K-Ar age measurement on a basal member of Andrew Bay volcano as

being less than 500,000 yrs but published no supporting analytical

data. Based on this date, Marsh considered Mount Moffett and its

parasitic cone as being perhaps no older than 150-200,000 yrs while

Mount Adagdak may be no older than 100,000 yrs.

Several new K-Ar age measurements were made on Adak rocks by

G. Brent Dalrymple as part of the present study and these are reported

in table 1. Three of the four age measurements on Mount Adagdak vol-

canic rocks appear to be of good quality and range from 140,000±

34,000 yrs to 342,000±17,000 yrs. The two andesite (76AMm207 and 211)

age measurements are consistent with each other but are both consider-

ably younger than the date on the dacite dome which also appears to be

48

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NWC TP 6676

of good quality. The opposite situation Is suggested by the field

relations; It should be emphasized that with rocks as young as these,

the upper limit of the K-Ar age dating technique is being approached.

The limited'number of age measurements together with the poor exposures

leaves us unable to resolve this problem. A further discussion of this

problem Is contained in the petrology section. The age measurements do

however, strongly suggest that the general range of volcanic activity

at Adagdak occurred between 100,000 and 350,000 yrs ago.

Only one of the age measurements from Andrew Bay volcano is of

good quality and that age (827,000±167,000 yrs) suggests that Andrew

Bay volcano is indeed the oldest of the three volcanic centers. This

sample was collected from a dome at the base of which hot springs

occur (fig. 1).

The age sample from Mount Moffett is from one of the young ande-

site domes on the east side of the volcano; the age, although not

of the best quality, suggests the dome is less than 250,000 yrs old.

The main part of'the volcano would be older, perhaps on the order of

a few hundred thousand years. The K-Ar measurements suggest that

volcanic activity at Moffett and Adagdak volcanoes overlapped and was

in part contemporaneous, a suggestion first made by Coats (1956).

Petrology

Mount Adagdak is the remnant of a small andesitic stratocone which

has gone through periods of vigorous dome-building activity in the

central vent area. Only the south half of the original stratocone

remains and the central domes are exposed and open to the sea along

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the north side of the volcano (fig. 1). Coats (1956) has suggested that

the stratocone Itself was built upon an older shield volcano composed

chiefly of basaltic lava flows iith a probable thickness of over 300 m.

These flows rest on a foundation of flat-lying tuffaceous sandstone

exposed In the sea cliffs on the east side of the volcano.

The lava flows in what Coats called the shield volcano are at

least in part composed of olivine basalt. In addition to olivine they

also contain augite, calcic plagioclase, glass, and accessory magnetite.

Chemical analysis of samples from these flows are given In table 3

(Nos. 46AC36, 76AMm211, AD') and confirm the basaltic character of

the flows with SiO 2 being <50 percent.

The composite stratocone consists chiefly of tuffs with subordinate

flows. They appear to be chiefly augite andesite In composition (Nos.

76AHm206, 46AC21, table 2).

The domes in the central vent area appear to represent at least

three major dome-building eposides. They are light gray In color and

composed of porphyritic hornblende-bearing andesitic dacite. The

phenocrysts are calcic plagioclase and oxyhornblende with a groundmass

of augite, plagiocalse, and altered glass(?). Chemical analyses are

given in table 2 (Nos. 76AMm205, 204, 207, and 46AC175) and show a

Si0 2 content of 61-62 percent. The domes are progressively younger

towards the north and material from the dome building stage In the form

of breadcrust bombs, debris flows, and mud flows mantle the western

slope of the volcano.

The history of the volcano as presented above Is somewhat at

50

--- - - - - - -N

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variance with the K-Ar measurements (table 2). According to the model

presented here, the volcanic rocks exposed on the slopes of the volcano

represent a pre-dome cone-building stage and should therefore be older

than the domes in the central vent. The K-Ar ages however, indicate

just the opposite.

Three possible explanations suggest themselves. 1) The sampled flows

(one on the west side, the other on the southeast side) may represent

younger events satellitic to the main volcano. Such a situation is not

uncommon, but in this case is not supported by either our limited field

studies or the mapping by Coats (1956).

2) The whole-rock K-Ar measurements are inexact. Although three

of the four measurements appear to be of good analytical quality, they

are close to the upper limit of the technique. The limited number of

whole-rock age measurements is insufficient to resolve the problem;

3) The dome rocks contain excess radlogenic argon for unknown reasons

and therefore give a spurious older age.

The geology and field relations do strongly indicate however, that

the volcano did evolve far enough to form a high level magma chamber.

The silicic dacitic domes were then emplaced from this high level

chamber.

Coats (1952) description of Andrew Bay volcano suggests It was

a typical andesitic stratocone composed of intercalated breccla, tuff-

breccia, and lava flows. Much of at least the north end of the volcano

appears from our brief examination to consist of remnants of andesitic

51

NWC TP 6676

domes and dome debris, including mnonolithologic breccia. Coats however,

also mentions the occurrence of olivine-hypersthene basalt fragments

as fragments in tuff-breccia high on the eastern side of the volcano.

V The material may represent part of the original andesitic-basaltic

stratocone.

Host of the andesite domes consist of highly fractured greenish-

gray, hornblende-aug!te andesite With a glass-rich groundmass. Chemical

analysis of samples collected from near the north end of the volcano

(Nos. 76A1m217A, 218, and AD72, tabli 2) show them to be typical

andesites with 56-57 percent ST0 2 .

Judging from the remnant of Andrew Bay volcano still existing,

the volcano did not evolve or differentiate to the stage that nearby

Mount Adagdak volcano did. No dacitic rocks were reported by Coats

nor did we find any such material.

Mount Moffett volcano is a large composite stratocone measuring

about 11 km in diameter and rising to an altitude of 1196 m. It Is

a typical andesitic volcano composed of intercalated flows and

pyroclastic rocks with a parasitic cone of basalt and several andesitic

domes on the eastern and southern flanks of the volcano. Because of a

combination of poor weather and a lack of helicopter support, relatively

little work was done on Mount Moffett during this study and most of the

aescription of the volcano Is taken from Coats (1956).

The composite cone consists chiefly of tuff and tuff-breccia with

angular fragments as much as 1.5 m across; a few lava flows occur near

the top. The pyroclastic rocks are composed of hornblende andesite

52

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and porphyritic basalt. Tuff-breccia beds are as much as 120 m thick

and are locally interbedded with marine boulder conglomerates.

The lower and earlier lava flows are olivine basalt in composition

(No. 46ACM8, table 2); later flows consist of hornblende andesite and

olivine-hypersthene basalt (Nos. AD44, 46AC275, AD49, table 2).

The domes on the flanks of the volcano are hornblende andesite

(Nos. 46AC174, 76AMm222, table 2) and olivine-bearing hypersthene

andesite or basalt. The parasitic cone on the northeast flank of

Moffett is composed of olivine basalt flows, 1.5-3 m thick interbedded

with coarse basaltic lapilli-tuff (Nos. 46AC158, AD36, AD39, table 2).

Gabbro and basaltic agglomerate fill the vent of thi cone.

Remnants of a tuff-breccia cone of hornblende hypersthene andesite

rests unconformably on the lava flows of the Moffett cone near the

summit and represents one of the last stages of activity of the volcano.

Hot springs

Waring (1917) mentioned the occurrence of hot springs on Adak

Island in his compilation of hot springs in Alaska and Fraser and

Snyder (1959) report hot springs occurring on the east side of Andrew

Bay. During the present study, hot springs were noted at 2 principal

localities about 60 m apart on the east side of Andrew Bay about

2 km north of Andrew Lake.

The host rock at both localities appears to be strongly fractured

and altered andesite dome rock. Numerous oxidized and altered zones

along the fractures attest to a long period of hot spring activity.

The southernmost spring issues forth at sea level (best observed at

53

NWC TP 6676

low tide) through beach cobbles near the foot of a small (15 m in

diameter) rock "knob" which is about 7 m from the sea cliffs. The

orifice of the spring Is completely covered by the beach cobbles

and there are no surface signs of a hot spring (i.e., algae, iron

oxide, etc.). Hot water bubbles up through the cobbles and Is

dispersed through them into the ocean. Only an occasional trace of

vapor calls attention to the presence of a hot spring. A water temp-

ature of 71 °C was measured in the warmest spot in the cobbles; no

estimate of flow could be made.

A small pool, about 1 m by 0.5 m and 45 cm deep, occurs in a

crevice of a sea ci;ff bench about 10 m away. This small pool has

a distinctive red scum of Fe203 and a temperature of 350C measured in

the mud at the base of the pool attests to its thermal nature.

The other principal hot spring area lies about 60 m north of the

first spring and they are separated by ragged point of rock sticking

out Into the ocean. The springs issue out of tight fractures In a

low flat bench carved out of the sea cliff and only a meter or so above

low tide. The springs occur over an area of about 15 m by 7 m and

issue from steeply dipping (600 S.) fractures striking N. 50-900 W.

A hissing sound is associated with many of the hot springs and fissures.

Temperatures of 59-630C were measured and red coatings of Fe203 are

again abundant. Some attempt has been made to make a small pool by

damming up one of the springs with cement.

Water samples were taken from both spring areas for chemical

analysis which are given in table 3. The waters are essentially

54

NWC TP 6676

brines which Is not surprising in view of their proximity to the ocean.

The high concentrations of silica and boron however, are much higher

than that found in sea water and are more typical of hot springs

associated with active volcanic belts. Bicarbonate and calcium are

also high and suggest leaching of volcanic rocks.

Water chemistry has proved valuable in estimating subsurface

temperatures, and the various techniques and approaches are described

by Mahon (1970), Fournier and Rowe (1966), White (1970), and Fournier

and Truesdell (1973). The most quantitative temperature indicators

have been shown to be (1) the variation- in solubility of quartz as a

function of temperature and (2) the temperature dependence of base

exchange or partitioning of alkalies between solutions and solid

phases with a correction applied for the calcium content of the water

(the Na-K-Ca geothermometer). There is some ambiguity and uncertainty

in both methods, and in any particular region, subsurface information

may be necessary to calibrate adequately, or choose between, the methods.

Lacking knowledge of subsurface reactions, we have calculated

subsurface temperatures using both the quartz solubility (assuming

conductive cooling) and Na-K-Ca geothermometers. For the quartz

solubility geothermometer (Fournier and Rowe, 1966), the equation is

(Fournier, oral commun., 1973):

og1 Cc;0 -(1.309 x 103/T)-5-19,-'1°90 02q) 13T-5 9

where T - temperature in kelvins, and

CS102 - concentration of silica in milligrams per litre.

For calculations of subsurface temperatures from Na-K-Ca concentrations

55

NWC TP 6676

(from Fournier and Truesdell, 1973), the eq.ation for temperatures

above 1000C is:

Log1 0(mNa+/mK+)+l/3log1 O( mCa+ /mNa+) = 167/T-2.24o

where T = temperature In kelvins, and

mNa+ = molality of sodium ion,

mK . - molality of potassium ion, and

mCa+ = molality of calcium ion.

For temperatures below 100°C the equation is:

logy0(mNa+/mK+)4/3log1 O( =Ca+/mNa+) = 1647/T-2.240.

The results of these calculations for the Adak hot springs are

as follows:

Geothermometer

Sample no. Quartz Na-K-Ca

76AMm220 186 0C 1870c

76AMm221 1750C (using 185 ppm SiO 2) 1820C

143 0C (using 110 ppm SiO 2)

The Indicated subsurface temperatures are relatively high for

Alaskan hot springs (Miller and Barnes, 1976) but similar to those

reported for some other Aleutian Islands hot springs. The tempera-

tures are about at the minimum temperature (1800C) thought necessary

to drive large steam-turbine generators (Muffler, 1973).

Geothermal Potential

We have made an estimate of the nature of the possible thermal

anomalies beneath Mt. Adagdak and Mt. Moffett using the "Smith-Shaw"

model (Smith and Shaw, 1975). This model uses an estimate of the

56

NWC TP 6676

probable volume of high level magma chambers and the age and composi-

tion of the most recent eruption from these chambers to deternnne the

probable solidification state of each volcanic system and its relation

to a 3000C isotherm.

The application of the Smith-Shaw model is illustrated graphically

for Mount Adagdak volcano (fig. 3) and Mount Moffett volcano (fig. 4).

The small volume, old age, and relatively primitive composition of

Andrew Bay volcano indicates-any-underlying -shallow-magma-chamber-

has long since crystallized and cooled; the hot springs along the

margin of the volcano are more likely relative to a thermal anomaly

under Adagdak.

The pairs of lines in figures 3 and 4 are drawn to represent a

spectrum of cooling models that identify igneous systems that are now

approaching ambient temperatures (systems above lines 5 or 6), systems

that may now be approaching the post-magmatic stage (systems between

lines 3 and 4), and systems that probably still have magma chambers

with a large molten fraction (points below lines 1 or 2). The pairs

of lines represent the effect of shapes ranging from slablike to

equant for different cooling model's. For all of these cooling models

the depth to the top of the magma chamber is assumed to be 4 km.

The Adagdak volcanic system depicted in fig. 3 is based on a

range in volume and radlometric age as determined in the present

study. The field covered by probably limits of error of volume and

age just intersects line 6 which is an estimate of the time required

before the central temperature of the solidified magma chamber has

57

NWC TP 6676

fallen to 300°C. The plot shown in fig. 3 is based in part on the

radiometric ages. If, as suggested by stratigraphic relations, the

dacite cone Is actually younger than the andesite flows, then the

thermal anomaly may be of higher temperature than shown.

On the basis of these geologic studies, therefore, a thermal

anomaly of some sort very probably underlies all or part of Mount

Adagdak. The temperature of this anomaly, however, may be relatively

low (i.e., much less than 3000C). The geochemical thermometry of the

hot spring waters is in good agreement with a temperature of less than

3000 C as they suggest temperat:ires of 175-1800 C. The geothermal potential

of Mount Adagdak volcano, based on geologic studies alone, can at the

present time be considered only as marginal in terms of electrical

energy; the possibility of energy available for space heating, however,

would be higher.

The situation at Mount Moffett is somewhat different than at

Mount Adagdak In that Moffett is a large andesitic stratocone with no

known silicic vents. The plot shown in fugure 4 is a tentative first

approach to the evaluation of andesitic cones that have no known

silicic vents but which may be evolving toward a high level system.

In other words, if such volcanoes have a high level chamber, what are

the restrictions on chamber size? The maximum size (area) is considered

to be a function of cone diameter. In this case an approximate size Is

estimated by analogy to Kanaton cone and caldera (area - 25 km2) on

adjacent Kanaga Island. The dome distribution on Moffett suggests

(if these domes were dacite instead of andesite) a possible area of

58

NWC TP 6676

about 32.4 km2 . We therefore assume a probable maximum size of 30 km2 .

If the age of the most recent volcanic activity on Mount Moffett

is approximately correct, then a thermal anomaly beneath Moffett is

possible although the original magma chamber has probably crystallized.

It should be emphasized that we have only a single K-Ar age determi-

nation from Mount Moffett and are tentatively assuming that Mount

Moffett was, or is, evolving towards a high level system.

59

NWC TP 6676

References Cited

Cameron, C. P., and Stone, D. B., 1970, Outline geology of the

Aleutian Islands with paleomagnetic data from Shemya and Adak

Islands: Univ. of Alaska Geophys. Inst. Research Rept., UAGR-213,

153 p.

Coats, R. R., 1952, Magmatic differentiation in Tertiary and Quaternary

volcanic rocks from Adak and Kanaga Islands, Aleutian Islands,

Alaska: Geol. Soc. America Bull., v. 63, p. 485-514.

Coats, R. R., 1956, Geology of northern Adak Island, Alaska: U.S.

Geol Survey Bull., 1028-C, p. 47-66.

Fournier, R. 0., and Rowe, J. J., 1966, Estimation of underground

temperatures from the silica content of water from hot springs

and steam wells: Am. Jour. Sci., v. 264, p. 685-697.

Fournier, R. 0., and Truesdell, A. H., 1970, Chemical indicators of

sub-surface temperature applied to hot spring waters or Yellow-

stone National Park, Wyoming U.S.A., In Proceedings U.N. Symposium

on the Development and Utilization of Geothermal Resources,

Pisa, 1970, Vol. 2, Part 1: Geothermics, Spec. Issue 2, p. 529-

535.

Fraser, G. D., and Snyder, G. L., 1959, Geology of southern Adak Island

and Kagalaska Island, Alaska: U.S. Geol..Survey Bull., 1028-H,

p. 371-408.

Hahon, W. A. J., 1970, Chemistry in the exploration and exploitation of

hydrothermal systems, In Proc. U.N. Symposium on the Development

and Utilazation of Geothermal Resources, Pisa, 1970, Vol. 2,

Part 2: Geothermics, Spec. Issue 2.

60

NWC TP 6676

Harlow, M. W., Scholl, D. W., Buffington, E. C., and Alpha, T. R.,

1973, Tectonic history of the central Aleutian Arc: Geol. Soc.

America Bull., v. 84, p. 1555-1574.

Marsh, B. D., 1976, Some Aleutian andesites: Their nature and source:

Jour. of Geology, v. 84, p. 27-45.

Miller, T. P., and Barnes, Ivan, 1976, Potential for geothermal-

energy development in Alaska - summary, in Halbouty, M. T.,

Maher, J. C., and Lian, H. H., eds., Circum-Pacific Energy

and Mineral Resources: Am. Assoc. Petroleum Geologists Mem. 25,

p. 149-153.

Muffler, L. J. P., 1973, Geothermal resources, In Brobst, D. A., and

Pratt, W. P., eds., Potential mineral resources: A geologic

perspective: U.S. Geol. Survey Prof. Paper 820.

Scholl. D. W., Greene, H. Q., and Marlow, M. S., 1970, Eocene age of

the Adak Island 'Paleozoic(?)' rocks, Aleutian Islands, Alaska:

Geol. Soc. America Bull., v. 81, p. 3583-3592.

Smith, R. L., and Shaw, H. R., 1975, Igneous-related geothermal systems,

in White, D. E., and Williams, D. L., eds., Assessment of geo-

thermal resources of the United States--1975, p. 58, 83.

Waring, G. A., 1917, Mineral springs of Alaska: U.S. Geol. Survey

Water-supply Paper 418, 114 p.

White, D. E., 1970, Geochemistry applied to the discovery, evaluation,

and exploitation of geothermal resources; Rapporteur's report:

U.N. Symposium on Devlopment and Utilization of Geothermal

Resources, Pisa, Italy.

61

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NWC TP 6676

5. 41

au a 0-

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low -c N C4 0 ?% >

00

0 0

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0 . % U C!a

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0 o c 0 c c 0 C; -- 0; C; a w

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0 4,

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C~~~ th - .

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NWC TP 6676

Table 2 .-- Chemical analysis of hot spring waters, east side of

Andrew Bay; analysis in parts per million (ppm).

76AHm220 76AMm221

S102 218 110 (215 w/o dilution)

Ca 1500 1300

Hg 70 110

Na 6800 6100

K 460 380

*HCO 3 420 430

S04 120 330

Cl 13500 12000

F o.45 0.55

B 87 70

pH 7.4 7.5

Temp. (meas.) 630C 710C

* Total alkalinity as HCO 3.

63

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NWC TP 6676

on co - r N - c0 W% C4 %a :N -N NN co V%

CU Ci Ci~ L0I!~%'.~o- Usn

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:I.~~- xw CinT0 r 0! 0 COON

10r- r- - - N

.4C CEi. M~0

3cl r-s 0% N N '0 n

0. a% -n -r ,

co 0 0 a %a -:r 0 inC!- - in i%0C- ... ..' ...............

%0 % N -T %a m' co m a% -T 0r C4 %D i S

%a7 0r% %a co 40 mn 0T in -

0T 7% in %0 U% 7% U! 0! Ii- l.7

'C' 0r r- ON' Go m % 0 0 - - S

> 7 %a I'% %a %a SD C - N ,%9- -c -N

0n X

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NWC TP 6676

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r% U%

mt. 0 %0 0 f*% N a% co N~ Nn am- I

C4 - c 0%

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p% C4 40 - % em co co 61% 6% 0coC % 00.t N % 1%a ' -T N4 t% C4 - 0

c 611 co 0% -T (0% am (0% V C

faU

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V1% w- a% 0

0%

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co (0% 0 *A a* a* .% co I . -.T

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-T a-

0; 0% 0n - 0 0 C U 0 0 0n0-

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NWC TP 6676

Table 3 (cont.) Description of analyzed samples.

Adagdak

46AC36 - Basalt flow 0.7 mile northeast of northeast corner of ClamLagoon (Coats, 1952).

76AMm21 - Basalt flow, near roadcut on northwest side of Mt. Adagdak.AD-14 - Upper andesite flow exposed in roadcut on southwest side of

Mt. Adagdak (Marsh, 1976).46AC21 - Andesite dome 1.2 miles southeast of summit of Mt. Adagdak

(Coats, 1952).76AMm206 - Andesite thick massive flow, sea-cliff on southeast side

of Mt. Adagdak.76A1m208 - Andesite dome, northeast side of Mt. Adagdak.46AC13 - Andesite lowest flow, sea cliff on southeast side of

Mt. Adagdak (Coats, 1952).76AMm205 - Dacite dome, north side of Mt. Adagdak.46AC175 - Dacite summit dome, Mt. Adagdak (Coats, 1952).76AMm204 - Dacite dome, north side of Mt. Adagdak.76AMm207 - Dacite dome, top of Mt. Adagdak.

Andrew Bay

76A~m217A - Andesite boulder in tuff-breccia, east side of Andrew Bay.76A~m218 - Andesite dome, east side of Andrew Bay.AD72 - Massive andesite flow In sea-cliff 1 km north of Andrew

Lake (Marsh, 1976).

Moffett

46AC158 - Basalt from parasitic cone approximately 0.7 km east ofsummit (Coats, 1952).

46AC48 - Basalt flow in sea cliff 1.7 km northeast of summit ofparasitic cone (Coats, 1952).

AD36 - Basalt flow from parasitic cone, bottom flow in sea cliff2 km NW of NW corner of Andrew Lake (Marsh, 1976).

AD39 - Basalt flow from parasitic cone of Mt. Moffett (Marsh, 1976).46AC174 - Andesite dome 3.2 km south of summit of Mt. Moffett (Coats, 1952AD44 - Andesite flow exposed along beach 3 km NW of NW corner of

Andrew Lake (Marsh, 1976).16AC275 - Andesite flow from composite cone 1.5 km NNW of summit of

Mt. Moffett (Coats, 1952).AD49 - Andesite flow 4 km NW of NW corner of Andrew Lake (Marsh, 1976).76AMm222 - Andesite dome east side of Mt. Moffett.

* Samples 46AC36, 46AC21, 46AC13, 46AC175, 46AC158, 46Ac48, 46AC174,46AC275 from Coats, 1952. Samples AD14, AD72, AD36, AD39, AD44,and AD49 from Marsh, 1976.

66

NWC TP 6676

-% '4

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NWC TP 6676

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NWC TP 6676

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NWC TP 6676

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07

NWC TP 6676

Appendix B

THIN-SECTION DESCRIPTIONS. SAMPLES FROM ANDREW BAYHOT SPRINGS AND KIKUGU WARM SPRINGS AREAS.

ADAK ISLAND

Date. 25 October 1982.Collecor: Jim Brophy.

Field Notes:Original number: 6.Locality: Andrew Bay Hot Springs.Occurrence: Grab-sample from the Fe++-stained highly brecciated zone at the

northernmost rock exposure (Brophy).

Questions: (1) Classification, (2) description of alteration.

Hand specimen description: Limonite-stained fine-grained igneous rock.

Microscopic study for classification:Petographer: J. A. Whelan.Texture: Porphyritic.Secondary structure: Brecciation, hydrothermal alteration.Mineralogy:

Phenocrysts:-Chlorite pseudomorphic after euhedral hornblende 25%, corroded. Up to+3 mm long.-Plagioclase, euhedral, zoned, 15%; some zones partially replaced bychlorite, sericite, and calcite. Up to +2 mm in size. Fractured.

Groundmass:-Plagioclase, euhedral to anhedral. 40%. Up to 0.05 mm in size.-Quartz, anhedral, 10%, 0.05 mm.-Calcite (?), 4%.-Pyrite, 1%, 0.01 mm.

Special features: Goethite coats the walls of a 1-mm fracture in this rock.

Classification: Propylitically altered andesite porphyry breccia.

71

NWC TP 6676

Date: 20 October 1982.Collector: Jim Brophy.

Field notes:Original number: 7.-ocality: Andrew Bay Hot Springs.Occurrence: Taken from south of the two small peninsulars in the hot spring

area. Seemingly the least altered rock in the area.

Question: Classification.

Hand specimen description: Andesite porphyry; grey; weathers brown; groundmassgrey. About 10% plagioclase phenocrysts, I to 2 mm;about 10% hornblende phenocrysts, I to 2 mm.

Microscopic study for classification:Petrographer: J. A. Whelan.Texture: Porphyritic.Original structure: Flow.Secondary structure: Slight deuteric or hydrothermal alteration.Mineralogy:

Phenocrysts:-Plagioclase (10%), euhedral fractured frequently showing several crystallogra-phic orientations. Zoned overgrowths. Cores An83-86 based on combiredalbite-carlsbad twinning.-Hornblende (5%); euhedral, frequently with rims of fine-grained anhedralmagnetite.

Groundmass:Average grain size under 0.05 mm.-Feldspar seemingly untwinned, cloudy, 60%.-Quartz: anhedral, clear, 20%.-Calcite (?), 5%.

Classification: Hornblende andesite porphyry.

Origin of rock: Flow.

72

NWC TP 6676

Date: 26 October 1982.Collector: Jim Brophy.

Field notes;Original number: 8.Locality: Andrew Bay Hot Springs.Occurrence: Altered rock from hot spring area.

Questions: (1) Classification, (2) description of alteration.

Hand specimen description: Fine-grained dense grey-green rock. Weathers tan; on sawedsurface, grey. A few fragments or plagioclase phenocrysts are visible,up to about 6 mm. A very few green euhedral hornblende phenocrysts(1 mm) cut by a few irregular epidote veinlets up to 1 mm. Onefracture surface covered with a black mineralization (oxides?).

Microscopic study for classification:Petographer: J. A. Whelan.Texture: Porphyritic.Original structure: Flow.Secondary structure: Hydrothermal alteration.M-reralogy:

Phenocrysts:-Plagioclase feldspar (25%), euhedral, zoned. A poor determination onalbite twins gave An50. Generally about 0.5 mm, but some up toseveral mm. Some sericitization and calcite in phenocrysts. Fractured.-Epidote and chlorite after euhedral hornblende (25%). About 1 mmlong. Fine euhedral to anhedral pyrite (19%) associated with theepidote bit also disseminated throughout the rock.

Groundmass:Appears to be a mat of small euhedral plagioclase (40%) with inter-stitial epidote (10%).

Origin of rock: (1) Volcanism, (2) brecciation and hydrothermal alteration.

73

NWC TP 6676

Date: 26 October 1982.Collector: Jim Brophy.

Field notes:Original number: 9.Location: Andrew Bay Hot Springs.Occurrence: Most altered rock from sea-cut beach area of the hot spring.

Questions: (1) Classification, (2) description of alteration.

Hand specimen description: Grey porphyry with small (1 mm) hornblendephenocrysts. Weathers tan. Black Mn oxide staining.

Microscopic study for classification:Petrographer: J. A. Whelan.Texture: Porphyritic.Original structure: Flow.Secondary structure: Hydrothermal alteration.Mineralogy:

Phenocrysts:-Plagioclase (15%). Euhedral about 4 mm. Corroded, partially replacedby epidote.-Epidote (20%) pseudomorphic after euhedral hornblende, corroded,about 0.6 mm.

Groundmass:- -Plagioclase, about 0.03 mm, 60%: with fine epidote, 5%.

-Pyrite in anhedral aggregates up to 0.6 mm closely associated withthe epidote pseudomorphs.

Classification: Hydrothermally altered andesite porphyry.

Origiin of rock: (1) Volcanic activity, (2) hydrothermal alteration.

',.

'C 74

C.

NWC TP 6676

Date: 19 October 1982.Collector: Jim Brophy.

Location: Kiguga Warm Springs.Original number: 3.

Questions: (1) Classification. (2) type and degree of alteration.

Hand specimen description: Hydrothermally altered breccia zone. Note FeS2 mineral-ization (Brophy). Well-cemented, very fine-grainedanhedral to euhedral pyrite. This thin section is of onerock type, presumably a rock fragment in the breccia.A sample of the cement (numbered 3A) is being thin-sectioned. Sample 3A is fine-grained, dense (barite issuspected), and contains limonite pseudomorphs afterpyrite. (Slide 3A cement is chalcedony).

Microscopic study for classification:Petographer: J. A. Whelan.Texture: Microporphyritic.Mineralogy:

Primary:Groundmass:

-Glass: 65%, 0.01 mm; containing 5% (of the total rock), shards0.01 mm by 0.002 mm. Appears to have been K-feldspathized,followed by sericitization.-K-feldspar: 5%, euhedral. 0.2 mm by 0.05 mm, sericitized.-Quartz: 5%, anhedral, 0.15 mm by 0.05 mm.

Microphenocrysts:-K-feldspar: 20%, euhedral from 0.25 to 1.0 mm. Fresh to almosttotally sericitized.-Plagioclase; 4%, up to 0.6 mm by 0.2 mm. Badly sericitized,shows oscillatory zoning.-Quartz: 1%, anhedral, unaltered, up to 0.3 mm.

Secondary minerals: K-feldspar (?), sericite.Introduced minerals: Pyrite, anhedral to euhedral, approximately 0.2 mm.

Special Features: This appears to be an ash-flow tuff which has undergonefeldspathization and sericitization along with the introductionof pyrite.

Classification: Hydrothermally altered ash-flow tuff.

Origin: (1) Volcanic: (2) brecciation: (3) hydrothermal alteration.

75

NWC TP 6676

l)ate: 19 October 1982.('ollector: Jim Brophy.

Location: Kiguga Warm Springs.Original number: 4.Occurrence: At the base of the clifl, close to the hydrothermally altered breccia

zone (sample 3) (Brophy).

Questions: (1) Classification, (2) evidence of geothermal activity.

land specimen description: Limonite-stained fine-grained rock. On a sawed surfaceit is a breccia, with light-tan corroded fragments, usuallyabout 3 mm but up to 25 mm in a grey cement.

Micr.)scopic study for classification:Petrographer: J. A. Whelan.Texture: Breccia.Original structure: Quartz vein.Secondary structure: Brecciation and resealing.Mineralogy: Fragments are quartz (29%), anhedral, up to 0.25 mm and sericite

(1%), on grain boundaries and in irregular patches up to 0.25mm in a matrix of very fine-grained (0.005 '.o 0.01 mm) quartz(68%) and sericite (2%). There are a few quartz veinlets up to 0.2mm cutting the rock. A trace of anhedral pyrite up to 0.2 mm ispresent.

Classification of rock: Brecciated quartz vein.

Origin of the rock: (1) Hydrothermal deposition of the quartz vein; (2) brecciation;(3) hydrothermal healing of the breccia; (4) minor fracturing;(5) healing of fractures with quartz.

76

NWC TP 6676

Date: 19 October 1982.Collector: Jim Brophy.

r Field notes:Original number: 5.

Location: Kigugua Warm Springs.Occurrence: Grab-sample from fractured and silicified wave-cut beach.

Questions: (1) Classification, (2) indications of geothermal activity.

Hand specimen description: Breccia consisting of chalky white corroded fragments(30%) up to 10 mm in grey matrix. Weathers tan.

Microscopic study for classification:Petrographer: J.A. Whelan.Texture: Brecciated.Mineralogy:

Fragments: Consist of anhedral, unaltered fine quartz (70%) up to 0.2mm in size and 30% sericitized euhedral K-feldspar up to Imm long. Cement is very fine-grained (0.01 mm) quartz.Trace of limonite after anhedral pyrite.

Classification: Quartz healed, brecciated rhyolitic tuff or tuffaceous sandstone.

Origin of rock: (1) Volcanic activity, (2) deposition of the tuff or tuffaceoussandstone, (3) brecciation, (4) geothermal solutions healing thebreccia by the depostion of quartz. The same solutions sericitizingthe K-feldspars and depositing pyrite.

77

NWC TP 6676

Appendix C

TEMPERATURE LOG, ADAK ISLAND DRILL HOLES

On 12 January 1978, a maximum recording thermometer was lowered to totaldepth of 995 ft in Observation Hole 1. The thermometer, left at depth for2.25 hours, gave a reading of 75'F.

Table C-1 is a record of temperatures from Observation Hole 2.

79

NWC TP 6676

TABLE C-I. Temperature Logging Data, Observation Hole 2.

Depth, T0 F, T°F. Depth, T°C, TOC.ft down up In down up

0 41.2 40.5 0 5.1 4.750 41.0 39.7 15.2 5.0 4.3

100 41.9 41.1 30.5 5.5 5.1150 43.5 43.0 45.7 6.4 6.1200 45.4 44.6 61.0 7.4 7.0250 47.3 46.4 76.2 8.5 8.0300 49.5 50.0 91.5 9.7 9.8350 51.4 50.2 106.7 10.8 10.1400 53.1 52.2 122.0 11.7 11.2450 56.5 54.5 137.2 13.6 12.5500 57.9 57.0 152.4 14.4 13.9550 59.7 58.5 167.7 15.4 14.7600 60.6 60.8 182.9 15.9 16.0650 62.6 62.2 198.2 17.0 16.8700 65.8 64.5 213.4 18.8 18.0750 68.5 66.4 228.7 20.3 19.1800 70.3 68.0 243.9 21.3 20.0850 72.7 72.5 259.1 22.6 22.5900 74.7 75.0 274.3 23.7 23.9950 77.0 76.6 289.6 25.0 24.8

1000 79.0 79.7 304.9 26.1 26.51050 81.3 81.5 320.1 27.4 27.51100 83.1 83.3 335.4 28.4 28.51150 85.5 85.8 350.6 29.7 29.91200 87.4 88.0 365.9 30.8 31.11250 90.0 90.5 381.1 32.2 32.51300 91.9 92.8 396.3 33.3 33.81350 94.4 94.8 411.6 34.6 34.91400 96.2 97.0 426.8 35.6 36.11450 98.4 99.3 442.1 36.9 37.41500 100.4 100.9 457.3 38.0 38.31550 102.9 103.3 472.6 39.4 39.61600 105.1 105.6 487.8 40.6 40.91650 107.2 107.4 503.0 41.8 41.91700 109.6 110.1 518.3 43.1 43.41750 111.8 111.9 533.5 44.3 44.41800 114.1 112.8 548.8 45.6 44.91850 116.4 115.3 564.0 46.9 46.31900 118.9 117.7 579.3 48.3 47.61925 118.6 586.9 48.1

Notes:1. Logged by R. Clodt and J. Neffew 24 October 1978.2. Average Gradients: 50-1900 ft-4.201"/100 ft; 15.2-586.9 m-7.60C/100 m.

80

k"

NW(' TP 6676

Appendix D

GRAVITY AND MAGNETIC FACTS, NORTHERN ADAK

Terr. corr.,c Complete Bouguer

Station tlevation, Gravity b 2.0 gm/cc anomaliesd gm/cc CorrectedID Lattitudea Longitudca ft gay, - - - magnetics,ID ft ngal Inner Outer Total 2.00 2.67 2.40 gammas

zone zone

LORAN 51 59.60 176 36.63 154.37 981417.41 1.33 .12 1.45 183.3 182.5 182.8 480981 51 59.53 176 36.67 152.55 981417.86 1.45 .12 1.57 183.9 183.1 183.4 484412 51 59.43 176 36.57 181.88 981415.66 1.44 .12 1.56 183.8 182.8 183.2 482903 51 59.35 175 36.43 229.08 981411.96 1.91 .12 2.03 183.9 182.7 183.2 477874 51 59.25 175 36.52 194.36 981414.57 2.34 .11 2.45 184.7 183.9 184.2 472845 51 59.17 176 36.68 199.19 981415.05 2.73 .12 2.85 186.1 185.3 185.6 473976 51 59.10 176 36.83 221.65 981414.55 2.31 .13 2.44 186.8 185.7 186.1 476057 51 58.95 176 36.88 234.34 981414.36 1.90 .15 2.05 187.3 186.0 186.5 479848 51 58.85 176 36.80 220.80 981414.52 1.80 .16 1.95 186.6 1853 185 e 478339 51 58.73 176 36.73 283.19 981410.12 1.68 .18 1.85 186.5 184.7 18,a 4776110 51 58.60 176 36.68 282.11 981409.81 1.47 .17 1.65 186.1 184.3 18"'.11 4797311 51 58.47 176 36.70 281.49 981409.18 1.70 .18 1.88 185.9 184.1 184.8 4758812 51 58.30 176 36.58 313.81 981406.24 .93 .20 1.13 184.6 182.3 183.3 47656

13 51 58.12 176 36.50 314.22 981406.14 .55 .21 .76 184.5 182.1 183.0 4832914 51 57.97 176 36.50 283.70 981408.32 .43 .20 .63 184.7 182.4 183.3 4838815 51 57.85 176 36.52 262.41 981409.89 .46 .22 .68 185.0 183.0 183.8 4845816 51 57.70 176 36.52 244.38 981411.11 .28 .22 .50 185.0 183.1 183.9 4853317 51 57.53 176 36.52 224.49 981412.59 .26 .21 .47 185.3 183.6 184.3 4840218 51 57.38 176 36.43 229.56 981412.34 .23 .20 .43 185.6 183.8 184.5 4832819 51 57.25 176 36.j8 225.31 981412.98 .A5 .17 .62 186.4 184.6 185.3 4836720=M8 51 57.20 176 36.32 219.64 981413.57 .30 .17 .47 186.5 184.8 185.4 48552M9 51 57.18 176 36.02 211.19 9814i4.90 .22 .18 .40 187.2 185.5 186.2 ...21 51 57.18 176 36.00 208.88 981414.85 .26 .18 .44 187.0 185.4 186.0 489422 51 57.15 116 35.67 204.74 981415.07 .21 .17 .38 186.9 185.3 186.0 4958423 51 57.12 176 3 188.85 981416.42 .21 .15 .36 187.2 185.7 186.3 48360M81: 51 57.00 176 3: 142.07 981420.80 .17 .14 .31 188.5 187.4 187.9 ...M8G 51 57.02 176 35 139.03 981420.92 .16 .15 .30 188.4 187.3 187.8 ...24 51 56.92 176 35.32 93.44 981425.59 .19 .15 .33 190.1 189.4 189.7 4853325=EA 51 56.67 176 35.30 41.68 981431.40 .08 .17 .25 192.7 192.4 192.5 ...BS2 51 56.73 176 35.07 10.29 981432.84 .19 .19 .38 192.0 192.0 192.0 ...BS3 51 56.65 176 35.08 8.28 981433.74 .12 .18 .30 192.8 192.8 192.8 ...26 51 56.57 176 35.30 13.07 981433.80 .15 .17 .33 193.4 193.4 193.4 4831127 51 56.43 176 35.38 11.98 981434.76 .14 .17 .31 194.4 194.4 194.4 4774728 51 56.27 176 35.38 13.32 981435.40 .22 .15 .3 195.4 195.5 195.51 4810629=BS6 51 56.30 176 35.52 45.00 981434.28 .15 .15 .29 196.4 196.1 196.2 ...30 51 56.27 176 35.68 63.39 981432.38 .23 .16 .39 195.9 195.5 195.6 47t26M2 51 56.18 176 35.82 132.73 981428.43 .60 .14 .74 197.1 196.3 196.61 ...

See footnotes at end of table.

81

NWC TP 6676

Terr. corr.,C Complete Bouguer

Station Elevation, Gravity,b 2.0 gm/cc anomalies d gm/ce Corrected

ID Lattitude Longitudea magnetics,

a d gft mgal Inn-; Outer Total 2.00 2.67 2.40 gammaszone zone

31 51 56.25 176 35.92 72.73 981431.62 .23 .16 .39 195.8 195.3 195.5 47699M3 51 56.33 176 36.23 99.50 981428.46 .40 .17 .57 194.5 193.9 194.1 ...32 51 56.38 176 36.45 68.42 981429.77 .12 .22 .33 193.4 192.9 193.1 4809333 51 56.55 176 36.70 75.26 981426.42 .21 .23 .44 190.4 189.9 190.1 48655M4 51 56.55 176 36.65 102.80 981424.39 .78 .21 1.00 190.8 190.2 190.5 ...GEN 51 56.67 176 36.55 80.94 981425.41 .20 .23 .42 189.6 189.0 189.2 ...34 51 56.73 176 36.65 83.65 981424.26 .24 .23 .47 188.5 188.0 188.2 4957535 51 57.02 176 36.52 36.43 981426.24 .28 .24 .51 186.9 186.8 186.8 4785036 51 57.12 176 36.75 20.13 981426.69 .38 .26 .64 186.2 186.3 186.3 4815537 51 57.13 176 36.90 22.52 981426.27 .59 .26 .85 186.2 186.3 186.2 5019138 51 57.23 176 37.05 20.99 981425.30 .95 .26 1.21 185.3 185.5 185.4 4777239 51 57.35 176 37.22 20.18 981424.53 1.44 .27 1.71 184.8 185.2 185.0 4804040 51 57.47 176 37.40 19.73 981424.34 1.13 .32 1.45 184.1 184.5 184.3 4700641 51 57.53 176 37.65 20.13 981424.44 .31 .33 .64 183.4 183.4 183.4 4818442 51 57.43 176 38.02 22.43 981423.52 .12 .32 .44 182.5 182.5 182.5 4838043 51 57.38 176 38.30 21.84 981423.29 .11 .41 .51 182.4 182.4 182.4 4704344 51 57.32 176 38.50 20.82 981423.09 .10 .45 .55 182.3 182.3 182.3 4746245 51 57.27 176 38.75 30.67 981423.23 .13 .47 .60 183.2 183.2 183.2 4741546 51 57.20 176 39.02 28.90 981422.23 .14 .51 .65 182.3 182.2 182.2 4915747 51 57.15 176 39.27 32.20 981422.06 .20 .60 .80 182.5 182.5 182.5 4729848 51 57.12 176 39.50 32.12 981422.00 .42 .65 1.07 182.8 182.9 182.8 4763749 51 57.10 176 39.78 30.32 981421.40 1.48 .67 2.16 183.2 183.6 183.5 4796250 51 56.97 176 39.87 20.80 981421.96 1.97 .70 2.67 183.8 184.5 184.2 4736151 51 56.80 176 39.77 23.27 981422.91 1.28 73 2.01 184.5 185.0 184.8 4777352 51 56.65 176 39.78 18.62 981423.82 1.46 .78 2.24 185.5 186.1 185.9 4786253 51 56.50 176 39.78 20.30 981424.77 1.23 .80 2.03 186.6 187.1 186.9 4792254 51 56.45 176 39.42 19.01 981425.45 .40 .72 1.12 186.4 186.6 186.5 5208555 51 56.40 176 39.08 22.15 981426.16 .24 .64 .87 187.1 187.2 187.2 4783156 51 56.33 176 38.88 25.90 981426.36 .17 .56 .73 187.5 187.6 187.5 4804457 51 56.20 176 38.70 25.61 981427.74 .12 .52 .64 189.0 189.0 189.0 5231158 51 56.12 176 38.58 22.35 981428.80 .17 .51 .68 190.0 190.0 190.0 4787059 51 55.92 176 38.38 19.66 981431.14 .14 .47 .61 192.4 192.4 192.4 4684160 51 55.77 176 38.38 18.82 981432.31 .15 .47 .62 193.7 193.8 193.7 4804261 51 55.62 176 38.47 1884 981433.77 .19 .48 67 195.4 195.5 195.5 4777462 51 55.35 176 38.58 47.70 981433.83 .33 .47 .79 198.0 197.9 197.9 4742763 51 55.15 176 38.53 139.12 981430.00 .30 .36 .66 200.6 199.6 200.0 4789464 51 54.95 176 38.50 180.67 981427.91 .26 .33 59 201.6 200.2 200.8 4860265 51 54.75 176 38.32 165 83 981429.91 .19 .31 50 202.8 201.5 202.0 4768766 51 54.62 176 38.15 151.49 981431.66 .19 .25 .44 203.6 202.5 203.0 4848867=AtJ2 51 54.52 176 37.95 148.83 981432.53 .12 .24 .36 204.4 203.3 203.7 4729368 51 54.53 176 37.72 191.18 981430.22 .22 .22 .44 205.1 203.6 304.2 47805E19 51 54.63 176 37.50 162.24 981432.03 .16 .22 .37 204.7 203.4 203.969 51 54.62 176 37.47 166.91 981432.19 .16 .22 .38 205.2 203.9 204.4 4665470 51 54.72 176 37.20 202.09 981430.29 .15 .17 .32 205.5 203.9 204.5 4786471 51 54.62 176 37.05 244.22 981427.87 .26 .16 .41 206.2 204.3 205.0 48310BSI9 51 54.58 176 36.78 169.75 981430.05 .74 .16 .90 203.8 202.7 203.1BSI8 51 54.70 176 36.45 165.02 981432.97 .29 .17 .45 205.8 204.5 205.0E14 51 55.07 176 36.25 279.88 981425.00 .38 14 .52 205.2 203.0 203.972 51 54.68 176 36.20 167.34 981433.20 .13 .13 .26 206.0 204.7 205.2 4761673 51 54.70 176 35.87 177.10 981432.47 .29 .13 .42 206.1 204.7 205.3 4810974 51 54.70 176 35.57 163.06 98!433.47 .33 .11 .43 206 1 204.9 205.4 4789875 51 54.72 176 35.32 82.41 981438.50 .22 .11 .33 205.5 204.9 205.2 48984

See footnotes at end of table.

82

NWC TP 6676

Terr. corr.,c Complete Bouguer

Station Elevation, Gravity, b 2.0 gm/cc anomalis gm/cc CorrectedD Lattitud Longitud-- - - - - -- - - - -- magnetics,

Inner Outer Total 2.00 2.67 2.40 gammaszone zone

E8 51 54.82 176 35.32 83.13 981438.84 .20 .11 .31 205.7 205.1 205.4

76 51 54.85 176 35.12 67.99 981438.81 .19 .12 .31 204.6 204.1 204.3 4849777 51 55.00 176 35.00 33.50 981441.23 .13 .13 .25 204.4 204.2 204.3 48395El0 51 55.12 176 35.12 10.15 981443.36 .21 .13 .34 204.9 204.9 204.9 ...78 51 55.13 176 35.15 12.52 981442.91 .23 .13 .36 204.6 204.6 204.6 4827979 51 55.50 176 35.10 11.33 981441.06 .36 .15 .51 202.2 202.3 202.3 4803580 51 55.35 176 35.15 10.29 981441.80 .64 .14 .78 203.4 203.6 203.5 4819681 51 55.63 176 34.98 9.12 981440.14 .17 .15 .32 200.8 200.8 200.8 4881082 51 55.88 176 34.97 13.29 981438.71 .26 .14 .40 199.4 199.4 199.4 4865183 51 56.08 176 35.20 9.59 981437.63 .25 .15 .40 197.7 197.8 197.8 4908584 51 56.18 176 35.18 16.41 981435.88 .18 .15 .33 196.2 196.2 196.2 4831385 51 54.43 176 38.05 111.29 981435.00 .14 .26 .40 204.5 203.7 204.0 4862586 51 54.22 176 37.98 75.33 981437.67 .15 .27 .42 205.0 204.5 204.7 4790787 51 54.17 176 37.80 35.94 981440.28 .17 .28 .45 205.0 204.9 204.9 4875488 51 54.18 176 37.57 44.25 918439.75 .15 .27 .41 205.0 204.8 204.9 48948C9 51 54.25 176 37.43 87.31 981437.15 .15 .24 .39 205.2 204.6 204.9 ...89 51 54.23 37.40 89.28 981437.16 .14 .24 .38 205.4 204.8 205.0 4879990 51 54.27 17 37.17 126.25 981434.66 .23 .17 .40 205.4 204.5 204.8 4988191 51 54.38 176 37.05 168.18 981432.46 .24 .16 .40 205.9 204.6 205.1 48224El I 51 54.42 176 37.02 164.77 981432.56 .21 .16 .38 205.7 204.4 204.9 ...

E3 51 54.52 176 36.75 181.56 981431.74 .29 .16 .45 206.0 204.6 205.1 ...E4 51 54.58 176 36.58 137.82 981434.67 .32 .16 .48 205.8 204.8 205.2ES 51 54.60 176 36.28 187.28 981431.76 .28 .12 .40 206.2 204.7 205.3 ...

E6 51 54.62 176 36.10 189.47 981431.28 .43 .12 .55 206.0 204.6 205.1 ...92 51 54.55 176 36.97 223.35 981429.22 .14 .16 .29 206.1 204.3 205.0 4816893 51 56.75 176 35.38 31.00 981430.32 .14 .18 .31 190.8 190.6 190.7 4801594 51 56.73 176 35.65 '44.09 981429.58 .08 .20 .28 191.0 190.7 190.8 48070OFF 51 56.85 176 35.95 67.70 981426.01 .12 .18 .30 188.9 188.4 188.6 ...95 51 56.83 176 36.28 95.74 981424.10 .12 .16 .29 188.9 188.1 188.4 52538RUN 51 56.82 176 36.40 70.53 981423.62 .49 .20 .69 187.1 186.7 186.9 ...96 51 56.88 176 34.98 12.21 918431.52 .31 .17 .48 190.7 190.7 190.7 4819197 51 57.02 176 34.85 5.68 981430.91 .36 .18 .54 189.5 189.6 189.6 4792898 51 57.13 176 34.77 19.05 981428.71 .42 .18 .61 188.1 188.2 188.1 4790299 51 57.27 176 34.32 6.92 981427.99 .38 .18 .56 186.3 186.4 186.4 48324100 51 57.22 176 34.10 7.18 981428.42 .27 .18 .45 186.7 186.8 186.8 48486101 51 57.08 176 33.90 7.85 981429.61 .12 .17 .29 188.0 188.0 188.0 48436102 51 56.95 176 33.88 8.39 981430.98 .08 .16 .24 189.5 189.5 189.5 48286103 51 56.78 176 3383 3.41 981d32.69 .06 .17 .23 191.2 191.2 191.2 48323104 51 56.65 176 33.77 3.32 981433.98 .07 .14 .21 192.6 192.7 192.7 48437105 51 56.50 176 33.67 2.24 981435.42 .04 .13 .17 194.2 194.2 194.2 49057106 51 56.37 176 33.55 18.04 981435.96 .06 .12 .18 196.0 195.9 195.9 48691107 51 56.22 176 33.40 16.84 981437.69 .05 .11 .16 197.8 197.7 197.8 49691108 51 56.12 176 33.27, 18.15 981438.68 .06 .11 .16 199.1 199.0 199.0 48447109 51 56.05 176 33.15 22.72 981439.07 .06 .10 .16 199.9 199.7 199.8 48611110 51 55.88 176 33.07 22.52 981439.08 .08 .10 .18 200.1 200.0 200.0 48693!11 51 55.73 176 33.02 8.49 981441.28 .13 .10 .24 201.6 201.6 201.6 48518112 51 55.75 176 33.27 5.70 981441.84 .03 .11 .14 201.9 201.9 201.9 48291113 51 55.67 176 3352 10.35 981442.46 .16 .10 .27 203.1 203.1 203.1 48459114 51 55.55 176 33.72 9.87 981442.57 30 .10 .40 203.5 203.5 203.5 47856115 51 55.33 176 3382 8.23 981443.21 .07 .10 .17 204.1 204.1 204.1 47861116 51 55.18 176 33.95 9.85 981442.88 .04 .11 .15 204.1 204.0 204.0 48246117 51 55.07 176 34.35 47.17 981440.19 .08 .10 .18 204.1 203.8 203.9 47927

See footnote, at end of table

83

~~~~~~~~~~~~~~~~~.. .. . ......... ,-.... .. ,:., .. . -,....- . .

NWC TP 6676

Terr. corr.,V Complete Bouguer

Station Lattituda Longitu.c t Elevation. Gravity.b 2.0 gm/cc anonlalies,Y gll/cc CorrectedID---------------------------------indignelies.ID ft rgal Inner Outer Total 2.00 2.67 2.40 gammas

zone zone

118 51 55.13 176 34.55 20.62 981441.95 .09 .11 .20 204.0 203.9 203.9 48393119 51 55.08 176 34.78 11.34 981442.05 .12 .13 .25 203.6 203.6 203.6 48244120 51 54.12 176 37.13 40.25 981439.60 .18 .18 .37 204.6 204.4 204.5 48588121 51 53.98 176 37.17 14.55 981440.00 .06 .20 .26 203.4 203.3 203.3 48749122 51 53.83 176 37.25 13.64 981439.53 .04 .20 .24 2030 203.0 203.0 48090G3 51 53.80 176 37.33 11.06 981439.22 .06 .21 .27 202.6 202.6 202.6 ...123 51 53.68 176 37.32 13.78 981439.39 .03 .20 .23 203.1 203.1 203.1 48258G4 51 53.60 176 37.32 14.17 981439.27 .03 .20 .23 203.1 203.1 203.1 ...124 51 53.48 176 37.45 12.49 981439.64 .05 .24 .29 203.6 203.6 203.6 45997125 51 53.30 176 37.58 19.33 981439.51 .04 .24 .28 204.2 204.2 204.2 48221126 51 53.15 176 37.60 17.65 981440.56 .06 .24 .30 205.4 205.4 205.4 48238127 51 52.93 176 37.57 37.80 981439.94 .18 .21 .38 206.6 206.4 206.5 50012J15 51 52.83 176 37.77 210.03 981427.33 2.47 .15 2.62 208.1 207.2 207.6 ...128 51 52.83 176 37.57 48.34 981439.50 .33 .20 .53 207.1 206.9 207.0 49974J14 51 52.77 176 37.65 37.65 981439.57 .18 .21 .39 206.4 206.2 206.3 ...J13 51 52.62 176 37.67 31.95 981439.79 .02 .21 .23 206.3 206.1 206.2 ...129 51 52.62 176 37.65 35.74 981439.69 .03 .21 .24 206.5 206.3 206.3 48645130 51 52.48 176 37.62 26.16 981441.03 .04 .21 .26 207.4 207.3 207.3 48141J12 51 52.43 176 37.62 23.27 981441.50 .39 .22 .61 208.1 208.1 208.1 ...131 51 52.32 176 37.77 20.44 981442.49 .45 .22 .67 209.1 209.2 209.1 48133132 51 52.15 176 37.82 31.29 981442.28 .17 .21 .38 209.6 209.5 209.5 48130133 51 52.00 176 37.98 21.61 981443.60 .06 .22 .28 210.4 210.3 210.3 47846134 51 52.00 176 37.75 21.10 981444.16 .11 .22 .33 211.0 210.9 210.9 47882135 51 51.97 176 38.78 22.87 981442.60 .04 .24 .28 209.5 209.4 209.4 48279136 51 51.97 176 38.60 23.62 981442.63 .04 .24 .29 209.6 209.5 209.5 47957137 51 52.08 176 38.48 29.68 981441.82 .05 .24 .30 209.0 208.9 209.0 47985H7 51 52.15 176 38.43 29.96 981441.58 .05 .24 .29 208.7 208.6 208.6 ...138 51 51.77 176 38.87 12.92 981444.29 .09 .26 .35 210.9 210.9 210.9 48235139 51 52.23 176 38.32 28.45 981441.71 .03 .24 .27 208.6 208.4 208.5 48485H6 51 52.27 176 38.30 24.28 981441.72 .03 .24 .27 208.3 208.2 208.2 ...H5 51 52.42 176 38.25 28.35 981441.13 .03 .24 .27 207.7 207.6 207.7 ...140 51 52.43 176 38.23 31.47 981440.75 .02 .24 .25 207.5 207.3 207.4 47212H4 51 52.60 176 38.18 32.08 981440.32 .03 .22 .25 206.9 206.7 206.8 ..141 51 52.65 176 38.17 38.23 981439.86 .04 .22 .26 206.8 206.6 206.7 48021H3 51 52.77 176 38.10 40.95 981439.50 .06 .22 .28 206.5 206.2 206.3 ...142 51 52.80 176 38.10 49.00 931439.02 .11 .21 .32 206.5 206.2 206.3 48410143 51 52.90 176 38.02 62.60 981439.46 .15 .20 .35 207.8 207.4 207.5 50173144 51 53.03 176 38.00 53.68 981439.74 .18 .21 .39 206.3 206.0 206.1 47662145 51 53.12 176 37.85 62.36 981438.20 .22 .22 .44 206.3 205.9 206.1 49658146 51 51.67 176 3912 18.09 981444.86 .25 .28 .53 212.1 212.2 212.2 48277147 51 51.75 176 39.28 55.72 981442.47 .20 .25 .45 212.1 211.8 211.9 48211148 51 51.93 176 39.38 40.12 981442.48 .50 .26 .76 211.1 211.0 211.0 47983AIO 51 52.03 176 39.30 35.74 981443.07 .15 .28 .43 210.9 210.8 210.8 ...J-12-5 51 52.07 176 39.50 56.01 981441.85 .25 .27 .51 211.1 210.8 210.9 ...149 51 52.13 176 39.48 47.41 981441.96 .28 .27 .55 210.6 210.4 210.4 48237A12 51 52.37 176 39.40 48.84 981442.70 .34 .28 .62 211.1 210.9 211.0 ...150 51 52.35 176 39.55 80.94 981439.81 .36 .26 .62 210.5 210.0 210.2 48005A13 51 52.55 176 39.42 28.66 981443.31 .26 .31 .57 210.1 210.0 210.0 ...151 51 52.55 176 39.63 48.82 981440.95 .45 .30 .74 209.3 209.1 209.2 47962A14 51 52.60 176 39.67 89.19 981439.32 .27 .28 .54 210.1 209.5 209.8 ...152 51 52.68 176 39.68 54.10 981440.57 .77 .31 1.07 209.4 209.3 209.3 48196L13 51 52.80 176 39.72 154.51 981434.78 .34 .26 .60 209.8 208.7 209.1

See footnotes at end of table.

84

. - : .- ,.,-. . , ? ...? , .-- -.? , .. . ? ,- . - .. - .*...- ,,.-.*...-. .*...*--.-...-,.-, .-.-- ,- . , ,.*..- -, . ,.

NWC TP 6676

"err. cLorr., c Complete Bouguer

r Staionl Elevation. Gravity, b 2.0 gin/cc anomalis, d gm/cc Corrected) Lattitud Longitud------------- -- magnetics,

!1I I regal inner Outer Total 2.00 2.67 2.40 gammas

zone zone

153 51 52.83 176 39.63 78.58 981439.03 .58 .30 .88 209.1 208.7 208.9 506291,12 51 52.93 176 39.52 118.51 981436.32 .31 .28 .59 208.7 207.9 208.2 ...154 51 52.92 176 39.30 40.71 981441.15 .50 .32 .82 208.4 208.4 208.4 48112155 51 53.02 176 39.13 79.42 981438.23 .25 .29 .54 207.7 207.2 207.4 48809LIO 51 53.12 176 39.12 148.38 981433.30 .51 .29 .79 207.6 206.6 207.0 ...156 51 53.13 176 38.93 73.59 981438.40 .17 .28 .45 207.2 206.8 207.0 50897L9 51 53.20 176 38.93 102.09 981435.77 .66 .27 .93 207.0 206.4 206.6157 51 53.28 176 38.70 60.00 981437.78 .25 .29 .54 205.6 205.2 205.4 49407L8 51 53.30 176 38.73 60.69 981437.93 .28 .29 .57 205.8 205.4 205.6158 51 53.50 176 38.60 92.98 981435.24 .29 .27 .56 205.0 204.4 204.6 47641159 51 53.63 176 38.53 110.71 981433.76 .34 .28 .62 204.6 203.9 204.2 48997160 51 53.80 176 38.48 125.40 981432.84 .32 .27 .59 204.4 203.5 203.9 49505B16 51 53.90 176 38.58 174.86 981430.05 .28 .26 .54 204.8 203.5 204.0 ...161 51 53.93 176 38.37 111.29 981434.60 .25 .27 .52 204.9 204.2 204.5 49964162 51 54.05 176 38.10 53.17 981438.80 .15 .26 .41 204.9 204.5 204.7 52341D2 51 54.10 76 37.93 20.55 981439.71 .17 .27 .44 203.5 203.5 203.5163 51 54.15 176 38.12 24.86 981440.61 .33 .31 .64 204.8 204.8 204.8 48532164 51 54.22 176 38.38 51.64 981438.37 .45 .35 .80 204.5 204.3 204.4 48136165 51 54.32 176 38.45 83.96 981435.92 .24 .34 .58 203.9 203.3 203.6 48146166 51 54.42 176 38.53 110.94 981433.66 .25 .34 .59 203.3 202.6 202.9 48012167 51 54.58 176 38.60 97.77 981433.81 .49 .35 .84 202.6 202.0 202.2 47781168 51 54.72 176 38.65 98.18 981433.12 .57 .38 .95 201.8 201.3 201.5 47947C2 51 54.87 176 38.68 120.34 981431.36 .32 .38 .69 201.1 200.3 200.6169 51 54.83 176 38.53 98.95 981433.04 .47 .37 .84 201.5 201.0 201.2 47413C3 51 54.85 176 38.47 171.17 981428.60 .35 .33 .68 201.8 200.6 201.1170 51 52.72 176 39.95 143.60 981435.81 .35 .26 .61 210.2 209.2 209.6 48020A16 51 52.70 176 40.00 157.52 981435.21 .25 29 .54 210.5 209.4 209.8 ...171 51 52.75 176 40.22 161.27 981434.90 28 .29 .58 210.5 209.3 209.7 48294172 51 52.67 176 40.43 169.56 981434.45 .31 .29 .60 210.7 209.4 210.0 48449173 51 52.57 176 41.02 322.73 981426.23 .17 .27 .45 213.0 210.4 211.4 48724174 51 52.67 176 41.05 344.18 981423.96 .22 .28 .50 212.1 209.3 210.4 48814175 51 52.88 176 40.93 377.39 981421.99 .48 .29 .78 212.3 209.4 210.6 48349176 51 53.08 176 40.97 504.84 981412.79 .85 .36 1.21 212.0 208.1 209.7 48469177 51 53.25 176 40.93 572.54 981407.59 .55 .40 .95 210.9 206.4 208.2 48934178 51 53.40 176 40.85 618.67 981403.69 .46 .43 .88 209.9 204.9 207.0 48921179 51 53.90 176 38.55 170.02 981430.48 .24 .26 .50 204.9 203.6 204.1 48832180 51 53.87 176 38.80 230.18 981426.24 .28 .25 .53 204.8 203.0 203.7181 51 53.77 76 39.07 318.22 981420.15 29 .25 .54 204.9 202.4 203.4 48376182 51 53.65 176 39.28 349.50 981418.70 .21 .29 .50 205.7 202.9 204.0 ...183 51 5'.72 176 39.55 410.07 981414.42 .45 .31 .76 205.8 202.5 203.8 48365184 51 53.58 176 3957 389.24 981416.85 .28 .28 .55 206.8 203.6 204.9 48642185 51 53.63 176 39.83 442.53 981413.06 .47 .32 .78 206.8 203.3 204.7 48896186 51 53.68 176 40.10 538.84 981405.16 .89 .38 1.27 205.9 201.7 203.4 48441187 51 53.70 176 40.32 596.22 981401.20 .77 .42 1.19 205.8 201.1 203.0 48498188 51 53.58 176 40.43 596.78 981402.96 .55 .39 .94 207.5 202.7 204.6 48379189 51 53.48 176 40.48 600.88 981403.68 .67 .39 1.06 208.8 204.0 205.9 48612190 51 53.47 176 40.62 639.30 981402.19 .60 .41 1.02 209.9 204.8 206.8 48405191 51 52.77 176 39.80 154.05 981434.80 .32 .25 .58 209.8 208.7 209.2 47630192 51 52.87 176 39.73 131.34 981435.97 .46 27 .73 209.4 208.6 208.9 47762193 51 53.00 176 39.65 159.28 981433.86 .47 27 73 209 1 207.9 208.4 47985194 51 53.13 176 39.83 267.42 981426.77 .49 .27 .76 209.2 207.2 20F 1 47676195 51 53.23 176 39.90 308.85 981424.04 .44 .27 .71 209.1 206.7 20",.7 47878

See foottiote,. at end of table.

85

. . " , . . . ° * w. °¢ ' ° ,O' '" .Do''° =" o ° o " ; 1 " - "° ' o " . . o ° . ,o " o. . " o-C. o ' .

NWC TP 6676

Terr. corr.,C Complete Bouguer

Station ttitud a Longitudea Elevation, Gravity,b 2.0 gm/cc anomalicsd gm/cc Corrected

ID Lattita ft mgal -- -magnetics,

Inner Outer Total 2.00 2.67 2.40 gammaszone ZoneI

196 51 53.33 176 40.05 393.64 981418.11 .37 .32 .68 208.8 205.7 207.0 48630

197 51 53.42 176 40.15 437.61 981415.22 .38 .33 .71 208.9 205.3 206.8 49157198 51 53.45 176 40.00 429.13 981415.60 .41 .32 .73 208.6 205.2 206.6 47882

199 51 53.57 176 39.80 398.61 981416.41 .27 .28 .56 207.0 203.8 205.1 4894.

200 51 52.33 176 39.68 92.69 981439.52 .29 .25 .54 210.9 210.3 210.6 48053

201 51 52.28 176 39.77 126.66 981437.47 .16 .23 .39 211.1 210.2 210.6 47903202 51 52.17 176 39.87 145.37 981436.23 17 .22 .39 211.4 210.2 210.7 48303203 51 52.07 176 39.97 157.11 981435.39 .15 .25 .39 211.5 210.2 210.7 48124204 51 51.95 176 40.20 146.91 981436.02 .23 .22 .45 211.6 210.5 211.0 48124

205 51 51.87 176 40.38 184.26 981433.95 .13 .21 .34 212.1 210.7 211.3 48331206 51 51.78 176 40.r5 207.59 981432.36 .20 .20 .40 212.3 210.7 211.3 48072207 51 51.68 176 40.65 215.47 981432.31 .13 .21 .34 212.9 211.2 211.9 48506208 51 51.57 176 40.77 240.99 981430.66 .16 .20 .37 213.2 211.3 212.0 47995209 51 51.37 176 40.73 232.14 981431.28 .20 .19 .40 213.5 211.7 212.4 48326210 51 51.27 176 40.72 283.59 981428.35 .21 .19 .40 214.3 212.0 212.9 48236211 51 51.15 176 40.68 284.61 981428.91 .28 .20 .48 215.2 212.9 213.8 48434212 51 51.02 176 40.45 248.43 981431.81 .91 .22 1.13 216.4 214.7 215.4 48385213 51 51.02 176 40.28 288.67 981432.84 .66 .22 .88 216.2 214.5 215.2 48126214 51 50.92 176 40.12 302.67 981428.86 .52 .20 .72 216.9 214.6 215.5 48232215 51 50.80 176 40.12 309.45 981428.50 .63 .18 .81 217.3 214.9 215.9 48527216 51 50.72 176 39.98 237.56 981433.29 .55 .21 .75 217.2 215.4 216.2 48512217 51 50.68 176 39.82 169.17 90)1437.55 .58 .24 .82 216.9 215.7 216.2 48664218 51 50.73 176 39.67 96.11 981442.23 .51 .29 .80 216.5 2159 216.2 48657

219 51 51.72 176 4n.98 282.21 981427.85 .11 .20 .30 212.9 210.6 211.5 48167

220 51 51.80 176 41.22 285.31 981427.89 .08 .20 .28 213.0 210.7 211.6 48356221 51 51.87 176 41.20 281.85 981427.67 .06 .20 .26 212.5 210.1 211.1 48229

222 51 52.10 176 41.18 293.00 981426.80 .08 .24 .32 212.1 209.7 210.6 48174223 51 52.22 176 41.18 297.84 981426.50 .10 .24 .34 211.9 209.5 210.5 48524224 51 52.33 176 41.12 328.37 981424.58 .13 .24 .37 212.0 209.3 210.4 48457225 51 50.83 176 39.55 76.54 981443.19 .53 .29 .82 216.0 215.6 215.8 48415226 51 50.95 176 39.42 26.44 981446.50 .50 .33 .83 215.7 215.7 215.7 48879227 51 51.10 176 39.35 21.72 981446.34 .38 .31 .70 214.9 214.9 214.9 48902AS 51 51.13 176 39.40 19.46 981446.33 .48 .31 .80 214.7 214.9 214.8 ...228 51 51.28 176 39.47 27.36 981445.24 .51 .29 .81 214.0 214.0 214.0 48992229 51 51.40 176 39.42 23.21 981445.19 .23 .28 .51 213.2 213.2 213.2 48403230 51 51.52 176 39.30 16.30 981445.35 .23 .29 .52 212.7 212.7 212.7 48199

231 51 57.37 176 35.98 213.57 981413.98 .16 .18 .34 186.1 184.4 185.1 48499232 51 57.52 176 35.83 236.15 981411.99 .26 .18 .44 185.6 183.7 184.4 48486

233 51 57.75 176 35.97 279.20 981408.73 .39 .20 .59 185.0 182.8 183.7 48374234 51 57.90 176 35.92 337.81 981404.50 .71 .19 .90 184.9 182.3 183.4 48526235 51 51.02 176 39.17 16.13 981446.91 .69 .32 1.01 215.5 215.7 215.6 48410F132 51 51.05 176 39.07 17.65 981446.70 .67 .31 .98 215.3 215.5 215.4 ...236 51 51.10 176 38.95 50.75 981444.63 .48 .27 .75 215.2 215.0 215.1 48408FB3 51 51.12 176 38.98 47.06 981439.15 .44 .27 .72 209.4 209.2 209.3 ...237 51 50.98 176 38.62 110.58 981440.98 .91 .23 1.14 216.2 215.7 215.9 48473238 51 50.97 176 38.28 111.02 981441.63 .33 22 .55 216.3 215.6 215.9 48714239 51 50.95 176 38.07 171.63 981437.34 .27 .19 .46 216.1 214.8 215.3 48565240 51 50.90 176 37.75 180.32 981437.80 .22 .19 .41 217.2 215.8 216.4 48145241 51 50.75 176 37.67 267.56 981432.96 .61 .17 .78 218.9 216.9 217.7 48624242 51 50.68 176 37.52 160.64 981439.43 .30 .20 .50 217.9 216.7 217.2 48424243 51 50.50 176 37.38 108.84 981443.05 .39 .24 .63 2184 2176 217.9 48721244 51 50.33 176 37.37 114.04 981442.42 .39 .26 .65 218.3 217.6 217.9 49217

See footnotes at end of table.

86

... .. .............. . .. . .... ......... .

NWC TP 6676

Terr. corr.,c Complete Bouguer

Station Elevation, Gravity,b 2.0 gm/cc anomalies, gm/cc Corrected

ID -Long e ft -magnetics,

1Lgft mgal Inner Outer Total 2.00 2.67 2.40 gammaszone zone

245 51 50.27 176 37.17 78.45 981444.96 .76 .28 1.04 218.9 218.6 218.7 49376

246 51 50.13 176 37.27 14.44 981449.53 .76 .35 1.11 219.4 219.6 219.5 49183

247 51 50.10 176 37.53 59.15 981446.60 .68 .33 1.01 219.5 219.3 219.4 50117248 51 49.93 176 37.63 9.12 981449.26 1.32 .39 1.71 219.6 220.1 219.9 49184

aLatitude and longitude from state-plane coordinates, AK Zone 10.bDrift-corrected observed gravity

CTerrain correction

dBouguer anomalies use post-1967 formula for latitude corrections.

87

NWC TP 6676

Appendix E

MERCURY CONTENT OF SOIL SAMPLES, NORTHERN ADAK

Sample Location Type Mercury content,no. (lat., long.) of soil ppb

WA-1-82 S Io559'40"l,17 603 6'40" Ashy 28WA-2-82 51 05 93 1 ",~ 1760 3 63 0?" Ashy 2WA-3-82 S51059'20?, 1 76036'2S"? Clayey 48WA-4-82 5 1059'05l, 176036'40? Clayey 110WA-S-82 5 1058'3S", 176036'30?? Clayey 179WA-6-82 51058'20"l 176036'30? Clayey 28WA-7-82 5 1057'501, 176036'30fl Gravelly 33WA-8-82 S51057'25"?,176036'30? Clayey 80WA-9-82 SI0S7h1 5"?, I176039'45"? Sandy 42WA-i 10-82 510~56'4S", 1760 39'50? Clayey 107WA-I 1-82 51056?25??,17603945?? Clayey 151WA-I 12-8 2 5 1056'20??,l 760381501? Sandy 129WA-13-82 S51056'10?,l76038'40"? 67WA-14-82 51055'30?,l76038'25? Sandy 85WA-15-82 51057'10?, 176039'20"l Sandy 13WA-I16-82 5 1057'20", 176038135"? Sandy 36WA-I17-82 51057'35??, 176037'501 Sandy 94WA-18w82 51057'20"l,176037'20? Rocky 33WA-19-82 S5I057?1001, 176036'40? 92WA-20-82 51l057?I5S",,I76036?05fl 73WA-2i-82 5 1 57?35", 176035'50fl Clayey 97WA-22-82 5 1056'45??, 176035'25?? Clayey 62WA-23-82 5 10~57'15", 176034135?? 190WA-24-82 5 105 6'401?. 17 60 3 515k Mucky 162WA-25-82 5 1 056'5 0l, 17 60 3 60 5 Ashy 0WA-26-82 5 1 0 56?35? 17 760 3 64 5 Ashy 62WA-27-82 5 105 6'2 0~ 17 60 3 6'15? Ashy 117WA-28-82 S510.36'10"1,17 60 3 5'2 0 Clayey 69WAw29-82 S 1 5 5'5 5 ", 17 6035'l 5?? Organic mucky 26WA-30-82 5 1055'35"?, 176035?l0"? Ashy 52WA-31-82 51054'55?, 176035'00?l Sandy 2

89

NWC TP 6676

Sample Location Type Mercury content,no. (lat., long.) of' soil ppb

WA-32-82 51055'10", 176034'20" Sandy 8WA-33-82 51055'20",1760 33'45" Mucky 1IWA-34-82 5 15 5'00",176034'05"l Sandy 24WA-35-82 51055'05",176033'30"' Organic mucky 63WA-36-82 51055'10",176033'10" Sandy 41WA-37-82 5 10 54'40",] 76035'15" Gravelly 19WA-38-82 5 054'40",1 1 76036'15" Sandy 44WA-39-82 .5 054'30", 176036'50 Clayey 152WA-40-82 5 154'30", 176037'05 " Sandy 31WA-41-82 5 1053'25",176037'25? Sandy 39WA-42-82 5 10 52'40", 176037'30"1 Sandy 6WA-43-82 5 105 1'20",176039'25"1 Sandy 27WA-44-82 51051'10".176039'25" Clayey 11!WA-45-82 5105 i'05",i 76038'5 0" Clayey 58WA-46-82 510 50'50",] 76038'15" Clayey 44WA-47-82 51050'55", 176037'45"1 Clayey 100WA-48-62 5 1050'25" , 176037'30" Clayey 62WA-49-82 51050'1 5", 76037'10"1 Clayey 35WA-50-82 51049'55",176037'45" Clayey 107WA-51-82 5 1050'35", 176039'15" Clayey 27WA-52-82 5 1055'00",1 76036'301 Mucky 98WA-53-82 5 1°54'40",1 76037'45 '" Mucky 109WA-54-82 51054'50",176036'50" 116WA-55-82 5 1054'45",176037'05" 15WA-56-82 51054'35",176037'55 " 109WA-57-82 51 0 50'25, 17603945 '" 60WA-58-82 5 1050 50",176040'10" 29WA-59-82 51 °54 ' 40 " , 1 76°38'30" 96WA-60-82 5 1055'00 , 176038251 Gravelly 49WA-61-82 5 1055V50",! 76039'25"' Organic 107!WA-62-82 5105 !'40",I 76039'20"1 Clayey 13WA-63-82 5 1052'45",176039'25"l Clayey 62WA-64-82 51 053'05", 176039'20"1 Clayey 51WA-65-82 5 1053'25",] 76039'001 Gravelly 25WA-66-82 5 1053'40" , 76038'50" Clayey 84WA-67-82 5 1054'05 ,l 176039'05 '" Clayey 52WA-68-82 51054'10",176038'55"l Clayey 58WA-69-82 51053'55",!76039'05" Clayey 115WA-70-82 5 1053'45 ',176039'30 '' Clayey 23WA-71-82 51053'50",176040'05 ' Clayey 56WA-72-82 5 105 '00" 176040'30 ' Clayey 19WA-73-82 51051 '50",1 76040'15" Organic 88

90

NWC TP 6676

Sample Location Type Mercury content,no. (lat., long.) of soil ppb

WA-74-82 S15 l1 '35",1 76040'20? Organic 115WA-75-82 5105 1'30",176040'40? Clayey 17WA-76-82 51051?0OI,176040'45u? 48WA-77-82 510511401?,176041?l5? Organic 50WA-78-82 51053?lO?? 17604015? Clayey 42WA-79-82 51-053'20 1 176041 '20" Clayey 35WA-80-82 5 1053145?, 1 76040140?? Gravelly 25WA-81-82 5 1O53'40"',l 76041 '25" Organic 31WA-82-82 51053'1 0",l 76041 '25" Clayey 40WA-83-82 510~53'] 01,176039'551 Clayey 79WA-84-82 S51053?50?l 176037'25"? Clayey 42WA-85-82 5 1054'l 0",l 76037'55"? 21WA-86-82 5 1054'30Ql 76037'35" Sandy 36

7-ADAGDAK 51058'45"?,176037'401 200 ft above 283springs

E-ADAGDAK 51058'45",176037'40"? At springs 54

Sample taken from just beneath tundra, Kikuga Warm 39Springs area

Sample taken directly from area of seepage at silicified 1 582zot.e, Kikuga Warmn Springs area

Sample taken 30 yards south of iron-stained silicified 31 6zone, Kikuga Warm Springs area

91

NWC TP 6676

INITIAL DISTRIBUTION

4 Naval Air Systems CommandAIR-01A (1)AIR-4106B (1)AIR-723 (2)

2 Chief of Naval OperationsOP-413F (1)OP-45 (1)

2 Director of Navy Laboratories (DNL)DNL-05 (1)DNL-08E (1)

8 Naval Facilities Engineering Command, AlexandriaFAC-03 (1)FAC-032E (1)FAC-04 (1)FAC-08T (1)FAC-09B (1)FAC-ill (1)FAC-iliB (1)FAC-1113 (1)

I Naval Facilities Engineering Command, Atlantic Division, Norfolk (Utilities Division)I Naval Facilities Engineering Command, Chesapeake Division, (Maintenance and Utilities Division)I Naval Facilities Engineering Command, Northern Division, Philadelphia (Utilities Division)I Naal Facilities Engineering Command, Pacific Division, Pearl Harbor (Utilities Division)1 Naval Facilities Engineering Command, Southern Division, Charleston (Utilities Division)5 Nasal Facilities Engineering Command, Western Division, San Bruno

Code 09B (1)Code 09C3 (1)Code 1(1)Code 1112 (1)Code 24 (1)

4 Naal Sea Systems CommandSEA-05H7 (I)SEA-070C (1)SEA-09B312 (2)

1 Commander in Chief, U S. Pacific Fleet (Code 325)1 Headquarters, U.S. Marine Corps (LFF-2)I Commander, Third Fleet, Pearl HarborI Commander. Sesenth Fleet, San Francisco3 Nasal Academ.r, Annapolis

Director of Research (2)Librar% (1)

3 Nasal Cisil Engineering Laboratory, Port HuenemeCommandim Officer (1)L70)PM. l)ase lolnes ()Technical Librar. (1)

92

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NWC TP 6676

2 Naval Energy & Environmental Support Activity, Port HuenemeCode 1101 (1)Code liA (1)

1 Naval Postgraduate School, Monterey (Library)3 Naval Ship Weapon Systems Engineering Station, Port Hueneme

Code 5711, Repository (2)Code 5712 (1)

1 Naval War College, NewportI Headquarters, U.S. Army (DALO-TSE)1 Chief of Engineers (DAEN-RDM)1 Headquarters, U.S. Air Force (AF/LEYSF)2 Air Force Academy, Colorado Springs

Code LGSF (1)Library (1)

I Air Force Intelligence Service, Boiling Air Force Base (AFIS/INTAW, Maj. R. Lecklider)1 Civil Engineering Center, Tyndall Air Force Base (DEB)1 McClellan Air Force Base (SMAL/XRE)

12 Defense Technical Information Center1 Department of Energy, San Francisco Operations, Oakland, CA (J. Crawford)1 United States Geological Survey, Menlo Park, CA (Library)1 Associated Universities, Inc., Upton, NY (Brookhaven National Laboratory)2 California Energy Company, Inc., Santa Rosa, CA

A. K. Carter, Administrative Manager, Compliance (1)J. L. Moore, Vice President, Exploration (1)

1 Geothermal Resources Council, Davis, CA1 Lawrence Berkeley Laboratory, Berkeley, CA1 Los Alamos National Laboratory, Los Alamos, NM (Reports Library)1 Oak Ridge National Laboratory, Oak Ridge, TN (Energy Division)I The Johns Hopkins University, Applied Physics Laboratory, Laurel. MD1 University of Utah, Salt Lake City, UT (Department of Geology, Dr. J. A. Whelan)1 University of Utah Research Institute, Salt Lake City, Ut (Earth Sciences Group)

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